I would say Grand Cayman. It's not as expensive as people think. My non-kiting wife and I just spent our honeymoon there in January. Flights are short from the US and not super spendy. Ours were $550 per person. Kiting there was excellent. I scored all but two days with most of the time riding an 8m or 12m. The water is amazingly clear.
For GF, the snorkeling was the most fun thing we did and it cost us zero.
If you want tons of restaurants, shops, 7 mile beach and Barkers beach to kite choose the west side. If you want quiet, more remote, very scenic and good kiting out of The Sweet Spot, choose the east side.
It was a great vacation!