Welcome to the suburbs.
Ming Tsai's Blue Ginger in Wellesley Square for interesting Asian food. I love the butterfish, and he has an great take on Lobster
Oga's in Natick (one town to the west) for wonderful sushi
don't let the strip mall location throw you off. People travel from Boston for Oga's food. Make sure to ask about the daily special sushi before ordering
also in Natick, Maxwells 148. Italian/Asian fusion shouldn't work - but it's surprisingly interesting (in a good way)
Alta Strada (Wellesley Square) family friendly casual Italian. Love mama Zucca's eggplant
Reservations recommended for all of these restaurants
My only complaint about Maxwells 148 is the GIANT bar television that can be seen from just about every seat in the place, which can make the place seem not low key at all. The food and service are excellent, though.
If you don't want to have the whole 2+ hour Blue Ginger experience, we love eating in the bar.
I've always found Alta Strada to be a solid go-to option in Wellesley dinner. It's Italian (not American-Italian). Also, they have a take-out lunch spot in the basement with great sandwiches.
Not sure if Brookline is out of the question, but its a short 20 minute drive from Wellesley and would open up a world of places as well.
Agree with the other suggestions here, and for lunch, Tutto Italiano in Wellesley Center has great sandwiches (proscuitto, capicola, etc.) Not a restaurant, but Wasik's Cheese Shop in Wellesley Center has a tremendous selection of cheeses (and Jamon Iberico). A really fun place to visit.