Hi, Leigh! I understand your dilemma, as my eight year old has quite the grown up appetite! Fortunately, there are quite a few all you can eat locations at Walt Disney World - and they don't all involve eating with characters!
For breakfasts, you can try Boma at Animal Kingdom Lodge, Chef Mickey's at the Contemporary, or the Maya Grill at the Coronado Springs resort, just to name a few. All of these meals are buffet style, and you can really fill up on all sorts of traditional breakfast fixings!
Lunch brings even more options, including the Biergarten at EPCOT, Hollywood and Vine at Disney's Hollywood Studios (which does have characters at lunch), or the Crystal Palace at the Magic Kingdom (also a character meal). If you are looking to go outside of the theme parks, you'll find a nice lunch buffet at Ft. Wilderness at the Trail's End Buffet.
Your options for dinner are all over the place! 'Ohana is a family style meal, all you can eat. Boma has a wonderful buffet, and the Liberty Tree Tavern is another very good family style meal. If you are looking for seafood, the Cape May Clam Bake has clams, mussels, fish and shrimp, plus a whole buffet of American favorites.
You can check out
www.allears.net for more information on dining options. If you click on the dining tab at the top, scroll down to look for the link on the left that lists all of the All You Can Eat meals.
Have a great vacation!