Carnival in Cozumel is very much a fun time for kids. You will be exposed to dances in the streets-- all with colorful dresses and such, but if you want to get away from that and spend some time snorkeling and touring the island, I would suggest a Tour. I have a 4 year old daughter and we went on this Dune Buggy Tour while we were there. It was great. We had our own car, our own tour guide, lunch, snorkeling, shopping, got a full view of the island. It was worht it and it made it easy on me and my husband... we didn't have to carry Kayla. when she was tired, she just went to sleep in the front seat and that was that. There are also multiple stops, so she didn't get restless. And for us it was a blast too!