I’d do no chairs at the cooktop island. Allow at least 24” for each chair at the table height island. And allow for generous aisle widths, like 5 feet from the table counter to the perimeter counter.

How many people do you need to be able to seat at the kitchen table?

Hire a kitchen designer to design a kitchen that meets your needs. There is more to kitchen design than an island.

@Mark Bischak, Architect is acknowledging what has been stated here many times…architects design great houses, but not great kitchens. You need a certified kitchen designer to design a proper kitchen. Any KD worth his/her salt, will be able to answer your questions.

Also you aren’t going to be able to vent that cooktop. i would put it on the wall. venting is wonderful!

No, I am not acknowledging that. The architect the OP has (if they are an architect) seems to not be well versed in residential kitchen design, and the OP should seek competent professional assistance in the design of their kitchen. Many architects are competent to design a residential kitchen in the houses they design.

This design has a restaurant like seating capacity. I can't see the living part that much. It should have at least matching capacity.

It seems like a fairly awkward setup to be honest. As others have stated, it would be helpful to get some outside help. While others may bawk at this, some cabinet companies have pretty competent  designers that could help you with your kitchen design for free.  If you have a builder and they already have a preferred cabinet company, that may be an option to work with even if you're early in your design.

Will you have another dining area? If not and you would like 8 chairs at the table, 9.25' will be a little tight unless you have small chairs or a pedastal instead of legs or waterfall at the end. (We had a 50" peninsula with an end panel and even with two small barstools, it was awkward to get in and out...we're small people too). If you need more seating and there's no dining room, I would add seating at the island too. I don't think it would look odd to have the table longer than the island either, so you can get the added length without making the kitchen longer. 25' is pushing it as it is, IMO.

Is there a reason you're putting the cooktop on the island? Can you post the plan of the first floor so far?

STOP NOW Get an independant KD before you really make a mess . No cooktop in an island where you will have seating anywhere for sure. Just because you see it in a picture does not make it right for your space . If you have that much space you have room for a proper table

Thank you so much everybody! You were very helpful! These are just photos I saw online as I'm looking for kitchen ideas at this point. I've gotten some inspiration from some friends who had a very long island with their huge gas stove in the middle of their island and I really liked it. My architect has not drawn up anything yet but he does have a floorplan that my husband and I sketched out. To answer some of your questions: I will have a pop-up vent for the cooktop which is located down inside the island when not in use. I currently have that setup and my cooktop is on my current island (it's on the end of the island, however). Below is a photo I found online of what it looks like when in use. There will be wall ovens located across the end of the island. I need extra seating for grandkids or for when we entertain. The table I am going to use in the new home has an expensive glass top and my chairs are white. This transpired because I need furnishings for my formal dining room. I also have a 4-seater glass table in my kitchen nook. I will not have a nook in my new home so my current formal dining table and chairs will be in the dining area of the new house, near the kitchen. There are several reasons why I want a table-height island attached to the longer island. A) I don't want grandkids painting at the formal table; B) So my husband can sit there facing the t.v. while he does his puzzles; C) I'm looking to match the amount of seating I have in my current kitchen area; and D) I need somewhere to do table-height projects. In the past people have done projects which ended up scratching my nook glass table top and I don't want that to happen to my formal dining table. I also wish to have the cooktop on the island because if I were to have a sink instead, the hard water being splashed will build up on the granite. I have that now at the back of my current sink which I'm always trying to remove. My new home will have hard water (future neighbors told us to be prepared for that). However, I will do whatever I can such as having a water softener and/or whole house filtration system. I also wish to have a hidden custom paper towel dispenser installed up inside a cupboard but if I had the sink on the island, I would not have any upper cupboards for the dispenser. I do not have paper towels showing in my current kitchen. In fact, the only things on my kitchen counters are minimal decorative items. I keep everything hidden.

My current formal dining area seats eight and my kitchen nook seats four. Plus, in my kitchen, I have island seating for five. That puts seating for nine in my kitchen area of my current home. When I move, because I will not have the nook table, I'm trying to acquire seating for at least nine like I currently have. If I did something like photo one then there is seating for nine. Also, I've always had a seating issue for holidays because I don't have enough seating for everybody in one room. Having the dining table near the kitchen islands will now put everybody in the same room for optimal conversation and I'm really looking forward to that! :)

This is what a pop-up downdraft vent looks like while in use:

I understand all of the reasons you want your long island with table height seating/workspace. I need a low counter for certain tasks too. But I still think you should reconsider the cooktop in the island. Although you're accustomed to a downdraft, a proper hood is superior in every way. You probably have enough room on the wall for both a clean up sink and cooktop, with a prep sink in the island. Have a kitchen designer take a look. I don't think you'd regret putting the cooktop on the wall run.

IMO if you are not willing to listen to actual KDs on here then just take what your architect gives you . Downdrafts are next to useless as venting for any cooking . Islands are the worst places for cooking but you seem to want that so have at er . You have a wealth of experinece for free on this site and if you don't want it then no one can make you do anything. If you really want help we need a to scale plan of the space with every measurement clearly marked , all windows door ways and where those doorways lead all need to be in the floor plan

When we remodeled our kitchen we installed a high-powered, exterior vented hood. It replaced an exterior vented microwave/hood combo.

Here's the thing -- I was so used to cooking with terrible ventilation I didn't realize how awful it was. Absolutely night and day. And what you're planning is even worse than what I had, because at least ours carried what little noxious fumes it did manage to move to the exterior of our house. The one you're considering doesn't even do that.

You're going to spend a substantial amount on your kitchen. Even though it doesn't seem like it, that "ventilation" system you're planning is equivalent to installing an oven that doesn't heat higher than 275° or a refrigerator that doesn't get colder than 55°.