David,
I have been to the Mayan Riviera twice. Stayed at the Rio Resort (5 star) and another resort which I cannot remember the name of. It was a 4 star at the beginning of the hotel zone. The area in general is very nice. Probably the nicest beaches in Mexico. As Mike mentioned, Cozumel is great for diving and snorkeling etc. Enjoy your trip and congratulations!
Cheers,
Shaun