No need to put a drainage pipe behind the wall. Make sure you put in a good solid base and use gravel behind each course to stabilize the rocks and reduce washout of soil behind the wall.

@ken - You can kind of see one of the white septic vents in the weeds a few feet in front of the deck and on top of the large retaining wall. It had to be put there (from my understanding) due to the drainage of our land. We put our home on 10 acres in the corner of one of our grain fields. Behind our home is a natural spring pond that eventually creeks off and feeds into a river about a half lv of a mile away from our home. We live in central SD. Our children right now are 2 and 2 months. Don't worry, I don't plan on ever having them unsupervised out there. We also have gates on both entrances of our decks. The plant choice is more for a deterrent/peace of mind since climbing a fence is pretty easy and fun for pour 2 year old. @Select - I appreciate the suggestions! I will look into those. I like the prickly idea. My parents planted prickly bushes in front of my bedroom window, I would assume to keep me in and the boys out, Hah! I doubt there are any codes due to the sparse population of our county, but I will certainly look into it! It is something I've thought of but forgot to research.

Use stone that is native to your area. Not only is it more appropriate, but also less expensive because of shipping costs.

1 - from a design standpoint it's easier to do them both of the same material. Making two different materials 14 ft apart look good isn't easy 2 - to tier or not to tier depends on that specific site and project. Keep in mind that if they're close to each other, two shorter walls are essentially acting as one taller wall. I'm currently redesigning a wall that was improperly built that way in July. I'm redesigning it because it's already failing and the center is leaning 15" out of plumb. Just because someone can stack blocks doesn't mean they can design a wall. 3 - the walkway *can* go up against the wall, but that generally isn't my preference 4 - six of one/half dozen of the other. If you're doing straight runs and no curves, poured might end up cheaper, but it depends. 5 - ehhhhh. The "stone look" walls aren't ever all that convincing. Rosetta probably has the best, but it's also a massive wall system. Where are you in VA that you have Unilock as an option? As far as I knew it's hard to get here. Wall blocks like Anchor or Keystone are almost bulletproof but they're nowhere near "natural" looking. At best they look like a Walmart parking lot built in the 2000s vs one built in the 90s. 6 - There are a couple of quality tiers among the block companies. I would say to let your installer help guide you (assuming they've done a fair number of walls). Some manufacturers are known for slightly less strict tolerances. A block being 1/8" out of square isn't a huge deal when there's a mortar bed. But with segmental walls, where you're stacking one right on the other, that means potentially grinding down every single block to keep the wall level. 7 - A standard timber wall is fine. The metal and timber one, I wouldn't touch without an engineered drawing because it sounds like what's keeping the wall straight is 100% the steel beams. 8 - work with a designer who is product neutral. You want the design that's right for your site, and then we start looking at which product gets that done the best. 9 - look for someone with a deep portfolio. There's a lot of "sure we can give that a shot" out there. This doesn't sound like something that should be someone's first decent sized wall project.