First thing I think of is all the City Walk clubs and bars that are there. Also, there is nice bars at the hotels as well. Clubbing is not my cup of tea, but sitting at a nice bar and having a drink and eats are nice. However, than that, that's all I can think of other than going on all the rides at USF / IOA you typically wouldn't be able to do with children, or without having to do child swap.
Oh! And this is not necessarily for just adults, but kind of something you wouldn't be able to do with small children and that is the VIP Tour at the Hard Rock Cafe. I say it wouldn't be for small children as it's quite a lengthy tour, or them potentially making a mess somewhere (specifically would be worried about the "white" room). However, it's one of those things you'd really get into if rock history is your thing and it's free.