You will find typical thanksgiving menu items at ALL WDW restaurants that day. I've heard Boma is a nice meal since you will find the standard turkey and fixings along with their regular menu items.
Remember not all restaurants will offer their regular menus that day. At Yachtsman's Steakhouse we were given a prefixed menu. They had a steak, turkey, fish, pasta entree to select from - but their regular menu was NOT available that day.
If you want variety, you're best bet is a buffet. If you want traditional T-giving dinner, you can find it anywhere - even in the food courts.