We did our own thing in Grand Turk. We like the beach and like to snorkel / dive. It is not hard to find a good beach. Just have to find what works best for you. If you like to have a good bar close by then they have it at Grand Turk.
I would rate this port as a big ZERO. We have been here before and found human crap on a very hot beach, very little shade to be found. We did not even get off the boat this time.
Took a cab to a beach out buy the light house. Cost too much for a cab. Take the bus it is only a few bucks per person verses 40 bucks for a cab. Only problem was we did not get there until 2pm.
We wanted to do a scuba excursion here but it sold out before we left Miami. Did not offer any other suggestions.
Best stop of all. Only problem is the cabs want to take you out the the beach that is about 35 minutes away at 50 bucks one way. We took a cab over to the man made beach at the resorts. Lions Head or something like that, closer to the cruse ship and had a good day. Nice beach, good snorkeling.