[gatour]

You will be fine. You will be told when you will be leaving to go back to the ship and where to meet up. Just keep track of the time in Grand Cayman and you shouldn't have any issues.

For Cozumel while I looked up your excursion and based on the desciption, I am guessing they will pick you up at the dock or very close to it by the catamaran and then dropped off at the same location. There probably won't being any shuttling by bus needed.