If you dock at Charlotte Amalie in St. Thomas (some ships dock out at the sub base, which means a taxi ride to get anywhere or a tour), you are within steps of the HAVENSIGHT MALL, which offers many of the same shops you will find downtown, which is about 2.5 miles or so. A brisk walk will get you there, but this may not be the best option for folks who don't tolerate heat very well or can't walk for extended periods. There's loads of auto traffic all along the route, but the harbor area is to your left and that is nice. Take a cab to Megans Bay or Sapphire Beach. You'll find lots of eateries along the waterfront area and lots of folks shilling for restaurant customers.
In St. Maartin, take a cab to any of the Dutch side beaches, which are very nice. Your ship will dock (or tender) right near the downtown if you just want to walk around. If you are more adventurous, you can take a cab to the French side where the seas are a bit wilder. Be aware that Orient Beach--a popular spot is clothing optional.
In San Juan,a short cab ride will take you to the beaches along Condado or Isla Verde--plenty of hotels and beach amenities there. Or if you like to walk and shop, head for Old San Juan, within walking distance of most of the ship docks.
Get advice on taxi fares from the ship (they'll include this info in handouts) and some ports post taxi fares on a big board near where you can get a taxi. I don't recommend restaurants in general because you never know if the same chef/staff/experience will greet others. We have enjoyed El Convento in Old San Juan for the setting and basically good food-- you might like it too.