I think the kids would enjoy either, they are both awesome atmospheres! But I would recommend 50’s PTC just because of how little they are. Sci-Fi is kinda dark, and a lot of the seating won’t allow all six of you guys to sit next to each other in the same booth, but you would be able to share the same car, which the booths are built into, unless you guys could get a larger booth. But Sci-fi is awesomeee. And as long as I can remember, I’ve always loved it. It’s such a neat experience, I always have a hard time picking between the two. But as far as the experience with little kids and the restaurants, my nieces and nephews like 50’s better, they don’t not like Sci-fi, but they ALWAYS talk about 50’s. The interaction are both are very entertaining, but in my opinion my nieces and nephews enjoy 50’s PTC more, the oldest is 4. The enjoy feeling like youre in your own kitchen, and all the little games and activities youre ‘mom’ (waitress) plays on you!
But all kids are different, and maybe with the ages they are at they would be satisified with just enjoying sci-fi cartoons on a huge screen and eating inside a cool car! But if your kids are more interactive, i.e. they’ll play the games with the waitresses and such, I think they’d enjoy 50’s better. It all depends on what kind of kids you had! But honestly, I do think either would be fun for a kid!
Hope it helped!