Thanksgiving Dinner w/o the bird
It's a little early to be booking Thanksgiving and many restaurants probably haven't even figured out their menus yet. Many restaurants will give you an entree choice so you can have fish, etc. instead of turkey.
But here's an OpenTable.com link:
As for ideas, Chinese and Japanese cuisine might be in order.
Here's some listings from last year that might help you with ideas:
kathryn is right - virtually all of the restaurants that have a T'day prix fixe offer about 5 different entrées including traditional turkey as one, plus one vegetarian, and then one or two meats and a fish. The same applies to Christmas. Check out the T'day menu at Cibo to get an idea of what almost all restaurants do: http://www.cibonyc.com/
767 Second Avenue, New York, NY 10017