As mentioned, they can all stay together in whichever space they want to play in. My 2 kids enjoyed the lab more than the club even though they were 4 and 7. The activities in the club are geared for the younger kids while the lab has activities geared for older kids. But, they can do whatever stuff they want. Try taking a look at some of the daily Navigators that people have posted to get an idea of what sort of activities they have.
My kids loved the lab for the following activities: Acids and Gasses science experiments, Flubber making, Magic show, Piston Cup racing, dodgeball, computer games, etc.