Looking for Wheelchair Accessible excursions in Costa Maya, Cozumel, & Roatan

[DKTexas]

We are travelling on Liberty of the Seas this November.  My family of 6 includes my teenaged son who uses a wheelchair.  We're looking for recommendations on affordable excursions in Costa Maya, Cozumel and Roatan that are kid, young-adult friendly & wheelchair accessible.  We don't mind skipping a formal tour and taking a taxi to a destination, but we are not sure if there are wheelchair accessible taxis in the 3 ports.  Does anyone have experience with the beaches, excursions, or self-tours?

Thanks,

Diane