crazyfamilycruisers, wise2u would know best, seeing that he was recently there.
Wise2u recommends Paradise Beach. Our family has also gone to Punta Sur Park in Cozumel. We've snorkeled and swam there. Not as decked out in amentities as Chankanaab, but, just as beautiful. It's a much quieter, relaxing beach. A local came around with a cooler selling us Pepsi and beers out of it, very reasonably priced.
I just googled Punta Sur Beach Cozumel and it came right up with photos and information. Check it out. You can't go wrong in Cozumel.