What can I do with my sister in South Florida?

My little sister is coming to visit me next week through the 4th of July. I've been living in the Miami area almost a year and know about tons of 21+ places to go like wet willies, Mansion, etc. but she's only 20 and doesn't have a fake (can't get one in time either). I know most of the family friendly attractions are up in Orlando, but are there any things I can do with her besides going to Space or Lincoln Rd. Mall and the beach? Maybe a good sight seeing tour or even a water park?