I would attempt to make an ADR for your party....and hopefully they will sit you together, I would assume that they would attempt that if you have an ADR for the people in your party.
As for those two restaurants, I have only eaten at 50's prime time and have to admit it was not my cup of tea. I know people love it there but for my family we did not care to be cajoled into eating all our peas.. We tried it once and have never gone back. Just not us, but people do love the interaction of the castmembers teasing the patrons of the restaurant, standing them up and making them sing songs if they do not eat all their food...so if you think that your 13 year olds would like that kind of interaction, I say go for it. The food is decent, place is cute, sci-fi we have never done. Just never interested us.
Hope others answer so you can get some more opinions.