Grand Turk: is only a mile wide by 6 miles long...we wanted to rent scooters/ended up with a golf cart. When you get off the ship walk outside of the gate(past the ship touristy area to the actual country) There should be people there renting scooters and golf carts...drive the island it's small...there is a lighthouse at the far end...that's about it! It was cool to see the animals (donkeys horses cows) roaming free!
Nassau I posted on that today under Other Ports.
Half Moon Cay...we did see people doing the horseback riding...they had fun! We went to pet the horses and walked the island and took pictures of the "sting rays" that was about it. If you have never parasailed that's fun/waverunners are fun as well. For excursions on Half Moon Cay book on the ship they seemed to fill up.