The most thrilling excursion that we ever did was a Helmet Dive in Bermuda. We don't swim well or snorkel so this was as good as it gets for us. My husband wears glasses and I won't put my head under water even when I swim. I read about it on the internet and booked by email before we left. The owner's name is Hartley and it's a family business that's been around for years. The Empress was docked at the Dockyard for two nights and we got a bus from there to Hartley's office. The third night we were docked in Hamilton.
Hartley takes you out a couple of miles to a shallow marked area that he visits. You get wet suits and a helmet (that fits over your head and on your shoulders) that traps air from the surface. He leads you around the ocean floor as you walk and kneel on the ocean floor while he points out coral and fish for maybe a half hour. You can't talk but he has signs. The fish are regulars and have pet names. We even touched a moray eel. Underwater stuff on TV gives me the creeps but I was determined to conquer my fear and was sooo proud of myself for doing this. For me, it was the scariest thing I've ever done.
We also bought the three-day bus pass, went to St. Georges, the lighthouse and climbed to the top (great views), Horseshoe Beach (no shade, brought our own umbrella), the caves, horse and buggy rides in both St. Georges and in Hamilton at night when we were docked there. We also parasailed (surprisingly tame) at the Dockyard, went to the glass shop... so much to see and do, but never ate off the ship as it is very expensive. Hamilton had a street party one evening where they shut down the street for local venders and music.
As you are docked in St. Georges, your parents should enjoy the courtyard at the dock and a horse and buggy ride that you can catch right there that takes you up a hill and has great views of the harbour. The driver talked about the homes and other things of local interest. There was no need for us to do an "island tour", because travelling on the local buses gave us tour enough.