Kennedy space centre is great fun. As you said you have 4 or 5 hours spare just to let you know Kennedy space centre looks a lot more bigger than it looks in the pictures and on
YouTube. I went last year for a day out and I was worried there weren't going to be much there but when I got there it was a lot more bigger than I thought it was and it's more bigger now because they got a new museum called gateway.
Anyway here are my favourite things to do.
Sliding down the NASA slides
Riding the simulator shuttle launch experience.
There's a movie theatre in the Shuttle Atlantis building which is on 4 walls and the roof and it's actually like as you in space and you see the star ship land them the doors open and the star ship is there and it's magical.
Gateway museum (New)
Rocket Garden
Get the free Kennedy space centre bus to the Appollo.
Watch the pre recorded show of the control room at the Appollo.
Imax theatre
ISS Triumph of technology crawling through activity
And there's lot's more to enjoy.
It's very difficult to do everything within 4 or 5 hours.