I highly recommend the following All-Inclusive resorts, all of which are family friendly with kid's clubs and plenty of activities to keep everyone entertained:
Club Med Cancun Yucatan-the best AI for amount of acitivities and very high food quality, however it is located far south in the Hotel Zone of Cancun at Km 20.5-21.
Riu Cancun
Riu Caribe
Dreams Resort-on site dolphin swim experience
Gran Caribe Real
Great Parnassus
Crown Paradise Club
The Palace Resorts group has a few resorts to consider as well including Cancun Palace, Beach Palace and the resort outside of the Hotel Zone known as Moon Palace.
I realize this list is quite lengthy however it is better to have more choices than only a few. I am sure you will find an appropriate resort for you and your family. If you need further assistance, please feel free to contact me.
Have fun planning your tropical family vacation in paradise,
212eric (AKA Eric Rabinowitz-Author)
PEOPLE'S CHOICE GUIDE CANCUN Travel Guide & Survey Book