I would suggest booking a tour for your first day in Bermuda to get a feel of the island and then decide where you want to go the other days. Don't book anything through the cruise line, they are too expensive. Horseshoe Bay is beautiful. The museum at the dockyard is great to learn about Bermuda and has some beautiful views. Crystal Caves and Swizzle Inn are close by each other. St George is a nice historical town. An excursion you can book at the docks Famous Homes and Hideaways is also fun. Don't try to do everything. If you are like most of us, you will come back to Bermuda many, many times.
Laura