We're going back to the Kennedy Space Centre, we only had 3 hrs last time, not enough. Ds, then 5, loved it, and dd 3, got enthusiastic b/c we were. This time my sis and I are doing the "Astronaut Training Experience", a full-day thing... Sis' family is going to Seaworld/Discovery Cove, 9 yo dniece is swimming with the dolphins instead of flying iwth the astronauts...
We visited the St Pete's/Tampa area twice on previous visits and it is lovely. We went to a state park south of St Pete's, don't remember the name, and dh stood in the water and watched a family of (wild) sting rays swim over his toes...very uncrowded, lovely. Haven't done Busch or Universal, though; maybe when the kids are older.
Shopping. Oh yeah.
I heard there's a good science center in Orlando, may take that in for ds, though he's thrilled by the Epcot Futureworld sciencey stuff.
Good question, have been interested in the other responses.