I cannot read details on your plan, but I have a few questions to start things off. Those better at this than I will follow.
1. Do you want to cleanup on the island? That is where the DW is, I think. And do you want to prep on the blank perimeter wall where the other sink is shown? I wouldn't.
2. Do you need two such large sinks? I wouldn't. A smaller sink on the island for prep, a single sink large enough for any cooking utensils for cleanup. I would not want a double sink.
3. Why not make the island wide enough for seating as you perhaps suggested? With the space you have, I would.
4. Are most of the base cabinets drawers?
5. Is there a pantry somewhere where you can store cleaning supplies--mops, brooms, vacuums? The 2 foot wide one seems skimpy.

Can you repost somehow so we can read the details on the plan?
Did your architect supply you with elevations? Can you post them?

I am with bellsmom, swap the cleanup to the perimeter and use a smaller prep sink in the island. And NOT right smack dab in the middle, lol! Besides, do you want all your dirty dishes and water noise on display there on the island? If it sits off to one side you have the option of laying out food or whatever when you are entertaining. And by all means, adding 15" for a seating area, you have the room!

I cannot read your details, but seriously consider a trash pullout somewhere, preferably your island where it is also in easy reach of your clean up sink and DW.