50s prime time is great if you get a good server. We had Loukili and he was AMAZING! Had us in stitches the whole time. However the food isn't that great (in my opinion).
For better food and great atmospheres I would 100% recommend Whispering Canyon Cafe. Also the high tea at the Grand Floridian is a really nice teen/adult experience. There's enough food to be considered a lunch. Also, I can never get enough of Ohana at the Polynesian. GREAT for dinner. Big tables, family style dining with giant skewers of shrimp, steak, turkey, pork. Hawaiian music. Also Boma at the Animal Kingdom Lodge. If you've never been over to the Lodge GO!!! It's so much fun. You can have fantastic African-inspired buffet (they have American food too) at Boma and then go watch animals at the Lodge's private savanna.
For all of these things I would recommend reservations.
Bon Appetit!