Hello Sandy, Tell us which islands you will be stopping at, and perhaps we'll be able to suggest some things to do on your own.
Most Eastern Caribbean island are pretty safe places. St. Thomas, for example has lots of stuff you can do on your own, and feel very safe. Just plan to arrive back at the ship with lots of time to spare.
Last year, we spent our stop in St. Thomas by catching a taxi over to Coral World. We just paid at the door, and spent the morning there. Then we walked directly next door to Coki Beach and spent the afternoon lazing on the sand, swimming and snorkling.
There are lots of taxis always available right there, so hopped in one for a ride back to the ship. Arrived with an hour to spare, so shopped around Havensight Mall for a while. (that is directly at the pier where the ships usually dock.)
If you are early risers, you can very easily take a ride up the tram to Paradise Point, to get a beautiful view of the island, before you move on to the rest of the day.
Lots of other things to do there.