Wow - this one's really divided opinions.
It is true that Busch does have the best collection of thrill rides in Florida - for the coaster junkies (like me - Montu is one of the best SLCs I've been on). However, I'm unsure what it would offer to your party.
Busch Gardens does, in my opinion, have the best animal exhibits. Going through the habitats on the train is excellent. That said, I've only seen Animal Kingdom briefly.
Again, from my brief experience of Animal Kingdom, BG has a lot less crowds and looks better, and is overall the more pleasant park.
Busch is definitely a park worth going to, and you may find some more grown-up rides that are suitable for your 5-year-old (they've got some intermediate coasters and other rides around, especially in the Timbuktu area). It is basically like Animal Kingdom, but better (at least in my opinion). Whether that's worth the trip (I think SeaWorld do a free coach service to/from the park) is up to you.