Mary in grand cayman you can go to the world famous seven mile beach. Go to stingray city and wade among them while feeding them. There is the green sea turtle farm and a rock formation that is called he**. You will be able to send postmarked post cards from there. The shopping centers are right where you are tendered in. There is also an atlantis submarine there that we take up tp about 44 people down to about 100 feet along the coral reef.
Cozumels has a lot of shopping, hard rock cafe, carlos and charlies, snorkeling and a bunch of other stuff.