Went to Cozumel last year with 2 six year old boys. We hired a driver and went to the ruins (pretty basic - it was super hot and the kids hated this part but I found it interesting and we wanted them to see something cultural), then to an outdoor restaurant on the ocean on the opposite side from where ship docks. It was good. We stopped by the chocolate factory but we were running low on time at that point so we just bought some chocolate and didn't do tour. Then we had our driver drop us at Dolphinaris, which we had booked direct and the price included pictures. It was a fun day.