I took my family to Cancun in April over spring break. We had a great time. Not sure if your into the night club but
http://www.cocobongo.com.mx/ is something to see. They do these shows which are truly amazing. My 16 year old daughter meet some girls down there that got us (my wife, me and her) into the VIP area and it was a blast. The place does not get going till around midnight and keeps going till 4 a.m. Jimmy Buffet's restaurant is pretty cool also. We took the kids 16 , 14 , and 10 to swim with the Dolphins at Atlantida (
www.parquenizuc.om), they had a great time. Enjoy your trip.