Hi 5thgirl. I have been to Aruba on three occasions and find that the beaches near to the port are windy and the surf can be heavy at times. We did Palm Island and had a good time there with beach activities and some snorkeling.
Curacao is really neat and you can walk from the ship to town and get quite a flavor of the area (the buildings are really stunning in colors) and do some shopping and see some great areas of interest. We have snorkeled the sunken tug and there were lots of beautiful fish but again, the surf is heavy and I would not recommend it for young ones. If I were going to spend my money, I would go to Trunk Bay on St John's, it is a great beach for all to enjoy. Also, you can grab an open air bus on St Thomas to Magans Beach and stay as long as you want and then get dropped off in town and do the shops and all. I have not been to Dominica. Hope this helps.