We've stayed at both Hyatt and Westin with w/ 6-8, 7-9 and 8-10 year olds: that is, every year for the past 3, and have been really pleased with the kids' program. Although for us it was more about other kids for ours to play w than anything else. We also found the counselors/caregivers to be excellent, and we found both the caregivers and other staff, e.g. waitresses looking for extra work, more than happy to offer evening sitting if we were looking for a night out w/out kids ( a good alternative to the planned programs).
I also know a nondiving woman who did a time share swap for Morritts on the east end, which is much less touristy, and her kids, 7 and 10, loved the activities. It is much more isolated as Drew says but I think it would be more "real" than touristy. You can always drive to G'town or 7 mile beach. The diving is supposed to be spectacular. Personally I'm looking forward to my next GC trip a no kids trip to east end.
Joe