I, too, would vote for Sci-Fi - the food is ok (and, to me, over-priced for what you get even when compared to other TS restaurants at WDW), but it is nice and quiet, super well-themed and fun to eat in a car and watch old movie clips.
DH and I also have eaten at 50's and I would say the server was really good at picking up on how much the table wanted to play or not play along. One of the tables next to us was really into it, but DH and I were kind of in the middle - our server gave us homework to do (which was actually fun), but I ordered double mashed potatoes in place of veggies (because I am NOT a veggie person either) and she said something like, "I'm in a good mood, so I'll let that pass" and then never said another word about it. If your family is super outgoing, they would probably love it, but when I am eating a TS at WDW I really want to relax from walking around so much and being on my feet, so that just isn't the ideal place for me.