There is 1 all inclusive in Grand Cayman called The Reef Resort. It is on the east side of the island (away from everything else). I have heard all good things about it. It is still expensive, but seems to be good value too.
I just booked 2 couples to Cozumel...3 of them were going to do their Open Water certs there. Some think Cozumel is not the place to go if you are just starting out, but it has a certain wow factor that can't be had in other places. I think it is quite safe....drift diving is the most relaxing type of diving you'll do. This was my first trip after getting certified as well (although I did get an AOW before going and actually did a drift dive specialty course while there). Cozumel also has a nice mix of everything...restaurants, shopping, nightlife, diving, and relaxation! Accomodations range from nice budget places to high-end romantic all-inclusive get-aways.
Turks and Caicos is one of my favourite locations. However, the good walls start in 50 - 60 feet of water. Frequent spottings of the bigger stuff like sharks and eagle rays. Seasonal humpback whales (Jan - Mar) are awesome...sometimes get to see them on surface intervals or in transit or if you're really lucky, while diving. There are plenty of other water activities there too. They have a couple of small casinos too.
Bonaire might be worth considering...very easy diving...either from boat or shore...but not much else. I hear diving in Curacao is comparable to Bonaire, but you can get more a resort-type experience mixed in with culture and history that Curacao offers...shopping and nightlife too.
Finally, I just returned from Little Cayman. If you want to do diving and nothing else, consider it. Bloody Bay wall has the nicest looking reefs and a nice mix of animal life too. The wall itself is very impressive. However, it depends on how you want your honeymoon to be....You will not find "romantic luxury" accomodations here.
Hope this helps, if you want any other specific info, feel free to send me a PM.
