Grand riviera Princess ------ It's awesome, it's got the room for your whole group to enjoy themselves, and plenty of activities to suit all the different tastes in the group.
Grand Riviera Princess All Suites Resort & Spa (Riviera Maya/Playa del Carmen, Mexico) - Resort (All-Inclusive) Reviews - TripAdvisor
I wrote a review of the platinum swim-up suites which are totally cool, it doesn't cost much to go platinum and for larger families in your group they have fairly inexpensive villas and multiple bedroom accomodations.
They have an in-house dive-op and a reef not far from the hotel. i wasn't a diver when I went there but snorkeled the reef and it was pretty awesome. The beach is rocky in the water, you need shoes to go in the water. the food is absolutely awesome and plentiful variety, and I mean PLENTIFUL VARIETY!!!
Anyway, I highly recommend the place and I know you'll very much enjoy it!