I'll second Tusker House for character buffets. I'm a vegetarian and found more to eat there than I did at most buffets. Most Disney TS restaurants are good for both vegetarians and meat eaters, but a lot depends on what your vegetarians like to eat. Some menus have pasta dishes, some have vegetable-based meals (salads, vegetable curries, etc.), and others have imitation meats. If you don't know how they like to eat, your best bet may be to identify some options and then ask your vegetarians (and maybe your meat eaters) to look at the menus.