Johanna:
If you asked my 9-year-old what his favorite restaurants at Disney World are, he'd tell you they are not in the park.
Chef Mickey's at the Contemporary tops his list because of its huge selection of cereals and pastries (not to mention a little extra special attention to birthdays). Because the aren't open for "lunch," make a reservation as late as you can on your day and you'll save a bundle over dinner. Ohana at the Polynesian comes in a close second because he tells me he can have as much steak and shrimp as he likes.
Of all the parks, Epcot hosts the restaurants that will stand out most in your son's mind, in my opinion. Teppan Edo is typically our go-to, because who doesn't love hibachi? But your party will be split up because the tables seat 8. Consider Coral Reef as a close second with its wall-length aquarium that will keep everyone entertained. Best of all, the menu offers a lot to like from steak to pasta and, yes, fish and seafood. For the same price as individual desserts, I'd recommend calling the cake hotline at least a week ahead at (407-827-2253) and ordering the Mickey Head Cake for the special occasion. It is one of their best values and is as yummy as it looks.
Wishing y'all a magical birthday and vacation!
Whitney