We stayed in the Aventura Spa Palace hotel in the Riviera Maya, it was bloody wonderful and the best holiday ever. However, it was adults only.
BUT. It is the only Palace hotel that is, all the rest are family friendly. One of the benefits is that you can use the facilites of any of them during your stay, incl an overnight etc. The Xpu Ha (I think) was next door to ours and about 20 mins in a taxi from Playa del Carmen. Taxis were hotel run and very cheap. PdelC is a lovely little town, very safe and even has a Senor Frog's!
The Xpu Ha is an Eco Resort and very family friendly. Has a great natural lagoon for safe snokeling, a real beach, a manmade beach, a river and pools. Accn is in wooden huts. AI, all mod cons. We would choose there for a family hol
The Riu Palace Riviera Maya is very good, met a family staying there and they were v impressed. All the usual Riu standards (for the Carribbean, Europe not so good) plus kids club, playgrounds etc. Again not far from PdelC.
Riviera Maya is lovely, very Eco friendly, they take it seriously over there. There is a fab Eco water park place called something like Xel Ha that we could have spent ALL our time at, was wonderful. Swimming with dolphins etc, but in the sea - free dolphins, not kept in a pool/aquapark. Cenotes, Chichen Itz, Tulum, it's amazing.
Cancun on the other hand...may as well be in America, too commercial, too busy, just doesn't seem like Mexico at all.
We went in Aug and it was bloody hot, but dry heat. Was in cancun before in June and it was sticky but
bearable.
Long, but HTH
I would go back tomorrow. I loved it there, hell I'd live there!