Well Im far from being an expert but I can tell you to be sure to add some type of drain at the bottom of the tank, if you read my post you will notice that I had a problem with drainage (due to my tank not having a drain) and the only water entering the tank was from a mister, also, if you plan on adding any critters be sure to match the critter to the type of terrarium you wind up with, dont try to mimic their habitat AFTER you get them, as for the jade plant, I think you will be fine so long as you dont set up a tropical tank, it might be to humid and wet for the jade =)

Not all tropical vivariums require a misting system. That being said, not all tropical vivariums require drains. A 2" layer of gravel at the bottom of the tank should work fine.

Any type of ivy would work great. If you have a nursury near you, go to the "houseplants" section and pick out some small growing tropicals. They will almost always do well in a terrarium.

Hes right, not all tropical vivariums require a misting system and not all tropical vivariums require drains, but if your kinda new to terrariums, I think it would be a good idea to add at least a drain as the most common way people kill their plants is by over watering them =)

Jades are extremely resilient, but they aren't the best long-term choice for a terrarium. You may want to stick to tropicals. If you want to set up more of a 'desertarium', then go ahead and use jade. Just make sure the humidity isn't too high and the substrate (soil) isn't too wet. A long time ago, someone with a lot of experience wrote a list of the best plants for closed terrariums (bottle gardens), which is what I kind of assume you are doing, since you said this is a children's project. That list has since been bumped off the end of this forum. but I saved it before it was. Here it is!

CLOSED TERRARIUM PLANTING AND CARE

Soil mixture
Do not fill the terrarium half-way up. Use as little mix as possible to give the effect you want. Styrofoam or other inert materials can be used under the mix to give height. The more mix you use, the more moisture it holds and the greater the chance of rot .
Use a mix that holds water and air, keeps plants firm, and discourages bacteria and mold. (Vermiculite holds water and air. Perlite holds air. Sand holds plants up). Use moderately coarse vermiculite alone, or a mixture of vermiculite and builder's sand or bird cage gravel. Or one third each of vermiculite, perlite and sand works well. Handle vermiculite carefully and wash hands well after use. When you water (see below), vermiculite will settle around the roots to hold a plant in place.
Keep as little of the plants soil as possible without breaking off too many roots. The small amount that is left will supply the plant with food for several years if the plants are kept within bounds. Do not use peat moss. It becomes waterproof when dry and requires too much water to rewet.

Do not press the mix down. Just firm material around plant enough to hold it up. Moist air needs to circulate through it.
Watering.
When starting your terrarium, water lightly around individual plants. Water will spread throughout mix by itself. Nature equalizes wet and dry. Once the humidity is properly distributed, roots will grow in the air and on the glass. Err on the side of too little rather than too much water. The terrarium should then be covered tightly with a transparent material such as Saran Wrap or glass. Wait at least one week to see if a condensation cycle starts.
If no condensation forms on the coolest side of the terrarium, during the day in very good light, add a few tablespoons of water a day until it does. Check to see that plants are getting enough light. (Inadequate light will prevent life cycles from starting.) If condensation forms on more than 1/3 of the glass, wipe it off with a paper towel and seal the top again. Do not leave it open to dry it. Plants that like high humidity will suffer. If excess condensation continues, repeat daily until only 1/3 condenses. When it is right, seal tightly, under the cover, with moistened Saran Wrap, and leave it in good light. A terrarium may go for a year or more without additional water if the proper balance of water and light have been reached, provided that it is properly sealed. You will need to open it only for housekeeping and trimming.

Mold and decay

Various molds may grow on dead material in the terrarium. Black thin little fibers with tiny spore heads may grow on dead leaves that are moist. If it does not appear to be spreading, leave it. This is often the fore-runner of moss, but may also mean the terrarium is too wet. White furry mold should be rubbed gently with a finger to disturb it as soon as it is noticed. Usually it will not persist if you rub it down a few times. Dead leaves should be left unless they are rotting against the glass. This will leave etched marks on glass that is hard to remove. If a lot of leaves are dying, give more light and wipe condensation out to make it dryer. The larger and taller the terrarium, the less likely there is to be trouble.
Insect pests
If you use materials from the wild, you may or may not want to prevent anything from hatching. (I love seeing what grows). Do not use collected wood (termites). When using wild moss (no soil), you may want to spray the back of it with a diluted liquid systemic insecticide (one that is absorbed by the plant roots). Use it sparingly and handle carefully. However, most things that hatch are easy to eliminate without chemicals.
Pests that come in on bought plants are harder to deal with, so examine all plant materials. You can use the systemic mixture on any soil around each plant if you think it is needed, but be sure to wipe out extra condensation that forms from the additional moisture. If plants are badly infected with mealybug or whitefly, it is best to snip off all leaves on the infected plant, wipe out most of the condensation in the terrarium, and wait for a healthy new crop of leaves. The result is usually satisfactory. Springtails are tiny white insects that jump around on the top of the soil when you water a plant. They are harmless and live on decaying matter so don't bother battling them.
Light
Light is the food of plants. "Plant food" is the equivalent of our minerals and vitamins. Without a good source of light, plants will gradually perish. A small terrarium cannot take sunlight because heat builds up too quickly in it. In a tall terrarium with a lot of air space this problem does not usually arise, and the sun can shine for up to three hours in the morning or late afternoon, and in winter at other times. (Moss, however, does its best in a very low, broad space like a punch bowl, with no sun.)
Do not move your plants around to follow the sun or to avoid it. Plants are oriented to the light and do not thrive if they have to repeatedly re-orient themselves. Do turn the terrarium gradually, over a period of time, if the plants are all growing to one side, or else tip the terrarium up to give the plants more even light.

Most flowering plants need sunlight to bloom, or at least to initiate bloom. Orchids and miniature sinningias and other gesneraids (members of the African violet family) can bloom easily if kept in a large enough terrarium. Keep gesneriads in small CLAY pots. They will not bloom if their roots are allowed to spread out. Use fish-tank pebbles or bird gravel to bury the little pots at an angle tipped towards the light so they will grow evenly. They need a bit of sunlight to start blooming, but usually keep it up for a long time afterwards. They will need occasional plant food and water if their pots dry out, but be sure to wipe out an equal amount of condensation.
Artificial light
Daylight in combination of fluorescent light is great. With fluorescent light alone, have the lights not more than 6 or 8 inches from top of terrarium. Incandescent light may add more of the red spectrum needed for bloom, but their red is hot. Keep the lights on up to 16 hours a day, preferably on a timer. Plants like regularity. On a fluorescent bulb, the 10 inches at either end gives inadequate light for many plants, so a set of 24" tubes alone does not have much good light. Under a 48" or 72" set of 4 bulbs, you can grow plants with high light requirements in the center, lower light at the ends. Judge adequacy by degree of etiolation (stretching). There are many new lighting systems on the market that provide much higher light and make growing under lights much more satisfying".

PLANTS IN A CLOSED TERRARIUM

What you DONÂT want in a terrarium

- Plants that grow too fast.
- Plants that need a lot of sunlight.
- Large-leaved plants.
- Plants that change character as they mature.
- Soil, which encourages the growth of bacteria.
- A too-fine-textured growing medium that packs down and discourages air circulation.
- Plantings that leave no space for plants to grow.
- Open terrariums that have to be watered, causing compaction of growing medium.
- Terrariums in colored glass that changes the spectrum of light.

What kinds of plants CAN be used?

* Plants that can be CUT BACK.
-Plants that have nodes along a stem rather than leaves that all grow directly from the surface of the soil. (Unless they are miniatures and very slow~growing.)

* Plants that DO NOT NEED SUN.
- Plants that need more than an hour of sunlight will stretch (etiolate), becoming vulnerable to rot, and outgrow the terrarium quickly.

* Plants that CAN TOLERATE HUMIDITY.
- FERNS - good and bad.

--Miniature ferns and slow-growing varieties are good, large-leaved and fast-growing are bad.
--Some are small but have large fertile fronds when they mature. (bear's foot, brake ferns,etc.)
--Boston fern is bad- too vigorous
Smaller, slower-growing varieties of larger ferns are good.
--'Fluffy Ruffles,' a miniature of Boston fern, has underground runners It is invasive but good where nothing else will grow.
- Club mosses. Selagenella, gold and green. Need bright light, no sun. There are many varieties of Selagenella, blue, very tiny, decorative.
- Wild mosses are a very useful cover for vermiculite or perlite, although they tend to grow up the glass (burned ground moss, found on rocks) or die off (velvet moss, found on damp, acid soil). If the terrarium is successful, offspring will appear in 1 to 10 years.

* Plants that GROW SLOWLY. These can be trimmed into the shape of miniature trees and shrubs for a landscape effect.
- Bella palm (Neanthe bella). Slow-growing dwarf, good when young.
- False aralia (Dizygotheca elegantissima). Excellent when young.
- Podocarpus. Very slow-growing, good.

* Plants that HAVE SMALL LEAVES.

-- Pilea varieties. Cannot take wet circumstances.
-- Creeping Charlie or English Baby Tears (Pilea nummularifolia). needs enough light or gets etiolated.
-- Baby tears (Helxine) - similar and dreadful without enough light.
-- Artillery plant (Pilea microphylla) Excellent.
-- Aluminum plant varieties: "Friendship Plant',"'Moon Valley etc. Not good. Leaves drop too easily.

* Plants to START in a terrarium, THEN MOVE when they get large.

-- Button Fern.
-- Rex begonia. Start from a single leaf, or part of a leaf with a vein.
-- Small-leaved Rex begonia. Leaf stem (petiole)gets very long, good in tall terrariums.
-- Miniature begonias. Begonia prismaticarpa. Need some sun to initiate blooming, then just good light.
-- Hairy varieties of Rex begonia do not do well in a moist environment.
Check with Begonia Society to get many wonderful varieties. Also African Violet Society for a complete world of gesneriads. Miniature African violets do well in a very tall terrarium, some sun.
- Runners of larger plants. Strawberry begonia (Saxifraga sarmentosa). Variegated varieties usually need more light to make up for lack of chlorophyll in white areas.

* Other SUITABLE PLANTS.

-- Pellionia varieties. Red-leaved plants need sunlight to penetrate through red.
-- Fittonia - large leaf, red-veined and dwarf white-veined.
-- Polkadot plant (Hypoestes) Leaves very thin, tend to rot.
-- Bloodleaf (Iresine) Green form OK.
-- Norfolk Island pine. Baby size good, slowgrowing.
-- Asparagus fern. Plumosa baby-size good, sprengeri too big. Trim regularly to keep small.

Credit goes to Diana Mae. I will personally vouch for the fluffy ruffles fern. It's awesome! Stays very nice and small, and looks so cute and fluffy! And do stay away from anything aggressive, like wandering jew and english ivy. They will take over a terrarium in no time.

Sahoy
Thanks for reprinting that post.Wonderful all around info. This is what most people think of as a terrarium.
A closed static system. I keep forgetting that they don't have top be complicated lol
gary