Relating to what Kelly said, the MCC Centra does not allow children under a certain age, high school-age I think, to be upstairs where all the workout equipment is. I don't know if they're allowed to be in the actual gym or racquetball courts unsupervised either.
If you intend to use the gym to shoot hoops etc., you do have to work around the basketball teams' practice schedules and a few other activities that take place in there, especially in the evenings.
Other than not really being "kid friendly," the Centra is pretty nice. They have different yoga and aerobics classes etc., too. Check out their website for more info. They do offer different memberships rates for individuals and families, as well as a 3-month or monthly options.