Beach alternatives Cozumel with 5 yo boy

[family cruiserz]

Hi -- We're headed for a quick cruise on the Radiance of the Seas to Cozumel next weekend. We usually just take a taxi to Paradise Beach then ride into town for shopping. We always have a nice time and my son has been happy to play in the sand and swim.(he's a great swimmer and snorkler). I'm afraid this time the weather may be a little cool and rainy (by our standards) and my son will be ready for something more. (it's his 11th cruise!) As we live in Florida (and in the water) a beach isn't critical. Has anyone had a successful (not outrageously expensive) non-beach day with their little guys? If we opt for something beachy, does Chankanaab have any covered area? Thanks so much