We went to KSC a month ago and loved it! My boys who are 7 and 9 thought it was very interesting even after doing Universal, an airboat ride, a boat ride through Wakulla Springs, beaches, etc. The bus tour is definitely a must.
We did it first thing in the morning and were well ahead of the crowds. It took us right past the vehicle assembly building where we could see the fuel booster waiting for the shuttle. It goes right over the road they move the shuttle over and we saw the vehicles they use to move it. The Apollo control building is also a driveby. One of the cool things on the bus tour is that they put the Apollo control room into a theatre and they stage a liftoff. The bus tour also brings you to viewing areas so that you can see the launch pads and has a place to touch a moonrock. We did just one of the IMAX movies, the bus tour, about 3/4 of the other presentations/displays and the nearby museum (which was very cool) in about 6 hours. The nearby museum has about 5 simulators at the end of it - very intense!
The ticket price was inclusive. Security was strict upon entering (they had metal detectors and looked through all of our bags, examined cameras, etc.) but there was no other "guarding" of things. Have a great time - Kennedy was one of the highlights of our trip and is still something my 9 year old speaks in awe of.