My two suggestions, I think, are a bit more off the beaten path for tourists, but my family loved them!
In Titusville, there is the Valiant Air Command Warbird museum. This is a great little museum with a bunch of old military planes and other memorabilia related to military aviation. The last time we went there, a veteran, who volunteers his time helping to restore some of the planes, offered to be our tour guide. It was simply awesome. So, if anyone in your family has an interest in aviation and/or the military, I highly recommend this little museum. You can find it on-line to get more information.
Another really fun thing we did was take an airboat ride. We went through Twister Airboat rides in Cocoa, FL, but I would imagine there are several companies that offer them. For us, it was really exciting to see all the alligators! We are from Montana, so just about everything in Florida is sooooo different from what we are used to. It was exciting!