The short answer to your unasked question is GO! You will have a great time. And bonus to create amazing memories of the trip with the grandchildren.

I cannot say that I have done much sailing in the USVI - though have done lots from land in St John. I am sure others can tell you about the dinghy options for the hot spots. If swimming is your weakness, get a Mae West or similar for when you are swimming to shore or snorkeling. It doesn't need to be inflated unless you feel you need it or get into trouble. If you are really worried about the boat sinking - not a particular concern of mine, but have met people who were deathly worried - then get something like this PFD and wear it while on the boat.

You'll have a great time! If you decide to go to the BVI, TMM is a great charter company to work with, or check out my boat Time Will Tell - I can give you a great rate!

Fair Winds!