It is safe. Cancun is fun although be prepared for how touristy it is. The water color is beautiful and the beaches are very nice (depends on the hotel as there has been a lot of beach erosion). Stay away from the Orbitz and other tour operators who hawk over the hotels. They are in general a rip off. Rent a car and drive south to Tulum with the family. The ruins at Tulum are spectacular. There are several nature reserves in that area that would be great for kids as well.

It sounds like you are staying away from all inclusive which is the RIGHT thing to do. We've stayed at the Le Meredian before (fantastic and quiet resort) and at the GR Solaris (awful inedible food and more of party place). Make sure to try the local food and street vendors. Tacos el pastor are amazing.