I went to cancun last year with my sister. We are (were lol) 29 and 27 at the time. Had an absolute ball! We aren't the partying type but we wanted a hotel that was going to have a bit of atmosphere during the day. We decided to go with the RIU Cancun and it did not disappoint us. It was wonderful. Food and atmosphere and staff were brilliant and great location!
There were kids at our hotel too.
We did a few activities. We swan with sea turtles which was fantastic. We also did the cenotes (but water shoes for this) we went to dolphin discovery and swam with sharks and manatees. Also went to one of the natural water parks with the zip lines. I think it was called xal something. I wished I went to another one. Wasn't as good as I thought plus you're only allowed on things twice!