Firstly I would like to say that the Space Center is really worth a visit. Depending on your interest in the space missions would determine which tickets to go for.

If like me you are a space nut, then I would recommend the 2 day all access ticket. This includes the Astronaut Hall of Fame and the KSC itself with all the tours.

If you are thinking of just one day, then there is enough to fill it at the KSC itself. Check out the NASA web site too, this gives much more info about launches etc.

http://www.nasa.gov/centers/kennedy/...sit/index.html