We've been to Iberostar Tucan, Iberostar Paraiso, and the Barcelo Maya, all on the Yucatan coast south of Cancun. All were very nice.
Our family's order of preference (Mom, Dad, two teenagers):
1) Iberostar Paraiso
2) Iberostar Tucan
3) Barcelo Maya
It's a wonderful vacation - you can make it as busy or as relaxing as you want!
Let me know if you have any further questions.