I could use some advice for a great spot along 7 mile beach in Grand Cayman for a bikini photo shoot. Any recommendations for a good spot? Any advice is greatly appreciated.

Thank you.

Whole beach to the high water mark (HWM) is public access. Most of the beach is also public, just a few hotels have it private to the HWM.
Quite a few smaller beaches around the island, all public to the HWM at least. Off SMB the beaches tend to be much quieter and secluded (except Smith Cove). Smith Cove is also a varied beach (sand, rock, trees). You could try Barkers National Park. Quite a few sections there that are very quiet (occasionally kite surfers, horse riders, dog walkers) but the sand gently shelves into the water, so you have more control over how deep the model gets (a couple inches to as deep as you want). SMB has a sharper transition into the water, but being so long (5.5. miles) you should be able to find gentle area.

If you want a pier, rocks, sand, heavily warped trees on the beach, let me know. Private beach (to which I have access, resort people still have access so it's not secluded) at the southern end of SMB. Fairly close to the Wreck of the Gamma if you want part of a shipwreck sticking out of the water as a backdrop.
Graham

Edited to add
No nudity allowed in public. A rather repressed island in that respect.
I also do some property rental on island, so I can do a good deal
Always happy to help a fellow photographer, if I have time I can help with transport (small van, single passenger in front, hang on in the back )

In the Cayman Islands, the National Weather Service today urged residents to monitor the progress of Irma, as it is still expected to influence local weather conditions when it hits this weekend.