I would check out the Kennedy Space Center at Cape Canaveral.
Be sure to do your research before going to Disney World. Get apps for wait times and look up the Extra Magic Hour schedule. EMH are times where the individual parks within Disney World either open an hour early or stay open a few hours late for on property guests. People end up either loving or hating Disney World. In the summer you should expect it to be very crowded and also that you will be standing in long lines in hot, humid weather. Bring ponchos as it will rain every day after 3:00 pm. It sounds bad, but knowing what to expect in advance does help.
If you are Harry Potter fans, be sure to go to Universal Studios in Orlando.
The beaches in general are much nicer on the gulf side. The water is warmer as well.
