At movie time (9 or later) each night the 3-4 and 5-7 groups are together. They lay down mats and show 2 movies each night. Other than that, it's a mix as to whether or not they're together. If you do some side-by-side reviewing of the navigators for the two age groups, you can see when they're in the same club.
My DS would sometimes get upset when we'd drop him off in the Club versus the Lab - it just depends on where the 5-7 group was at that time. He called the club "Her club" and the lab was "his", but they do switch back and forth