Wonderworks in Orlando is a great place - and kids love it:
"Housed in an upside-down building, this fun-filled venue simulates earthquakes and hurricanes, contains laser-tag facilities, allows you to design your own roller coaster to ride, provides the opportunity to swim with sharks and much more. "
Or for about $37 per person when you disembark the ship you can go to the Kennedy Space Center (I think the kid pricing is a bit cheaper).