gocruz...Rent Yourselves a Smart Convertible or a Scoot Coupe from Specialty Cars on the pier and drive around to the other side of Cozumel...there are some mighty nice (and remote beaches) and some great Beach Cantinas with Mariachi Bands (no charge to use the beach as long as you are having cocktails and munchies) ...You can't get lost if you stick to the main road and keep the sea on your right hand side!! Eventually you will also get to see the San Gervasio Mayan ruins(for a Fee). Returning you will also get to pass thru San Miguel for shopping!
A fun way to explore the entire island and easily done in 4-5 hours. Car rental is roughly $80 US with full insurance.