If your going to be in Magic Kingdom, i'd vote for Crystal Palace..it is another buffet mea, BUT different characters - its Pooh, Tigger, Eyore and Piglet - i've eaten lunch at Crystal Palace and really enjoyed it! and i'd say if your in Epcot Garden Grill is a good choice!
have a great trip!
oh and make the day more magical if in the magic kingdom bring your son to the barber shop near Crystal Palace - they will spray pixie dust in his hair really cool!
lisa