Don't know how long you will be there, but if you don't mind renting a car (driving in Mexico is not that bad) I would recommend going south to Playa and even to Tulum. When you get out of Cancun life really slows down. Lots to do and see and the beaches in Tulum are great.
Playa is about 30 -45 minutes from the airport and Tulum maybe another 45 minutes. Worth the effort