All pretty low key stuff. Some places have bikes available to borrow. Walk or hike. Birdwatch. Read a book. Hang out at beach/pool/hottub. It's usually possible to get a massage. There's a couple tiny museums. You could kill 20 minutes in the gift shop at LCBR. The hotels are small but may have a few things to do, like LCBR has darts, bumper pool, basketball/tennis court, volleyball net, kayaks to rent, exercise room. Sounded like we missed a good party at the Hungry Iguana on Friday night last time we were there. Karaoke one night at LCBR, though seems most people staying there would prefer peace and quiet.
Grand Cayman is civilization with lots of restaurants, shopping, boat and sub cruises and other stuff on the water, the turtle farm, botanic garden, and a other few touristy places to check out. Mini and regular golf, assuming they're open again. Worth taking a drive around the island.
