I'd consider the diving to be better if it generally met the following criteria:
- good visibility, 50+ typical
- warm, near 80F preferred
- fishy and high probability to see eels, shark, turtles, octopus
- not interested in tiny creatures and macro
- schools of fish are highly desired
- want dives to be at least an hour; so shallower helps and/or availability to get 100CUs
The additional criteria is that the location has a very good, calm beach for young kids.
Fish and a good calm beach are what stand out to me as your most important criteria for a family trip with a few dives snuck in. Not sure what type of accommodations are important to your wife and I'm guessing by the number of dives you get in per trip, your vacation generally lasts 1 week. Here are some thoughts:
Revisit St. Croix: Cane Bay has a very nice protected beach although there are others - can also scuba the wall there. Frederiksted, on the west side, is generally calm water year round. Dive sites Aquarium and Swirling Reef of Death (just a scary name) are fishy reef sites. The Frederiksted Pier is considered a highlight to dive and is an easy shore dive - can see various life. Nep2une Dive op is very good and across from the pier. Enough to see and do on the island for a week other than diving. Some rentals would give you your own personal beach. I've seen a lot of life (octopus, rays, eels, turtles, puffers, starfish, reef fish) just snorkeling on the west side.
Cozumel: one of my first thoughts, but may not be as fishy as you want. Drift diving may hinder your photography ability. Still great diving. The nice swimming beaches are on the south end of the island and generally at the AI resorts. There is some sightseeing - nothing, IMO, super-fantastic for kids though. Plenty of great dive ops to choose from.
Bahamas: Have only been to Grand Bahama. Only a few dive ops available. There are some good dive sites, but in the times I have been there, I've repeated several sites - was dependent on the op and the weather. You'd probably like shark junction for the number of sharks that swim around but I've yet to see a real fishy site. There are plenty of beaches, but, IMO, not nicer than St. Croix, Coz, or Grand Cayman. There is not much to do in the way of entertainment, especially for kids, again my opinion.
St. Maarten: Not normally mentioned as a top diving spot. Hit or miss on the diving dependent on the sites visited - which is true of many places. The first time I went, the wrecks were great, with variety of life, but swimming over sand wasn't exciting which seemed like what we did quite often. Second time, I stayed and dove a different part of the island (rather near a different bay.) I liked the diving better (various topography), but it wasn't super fishy. There are some beaches, not necessarily the more well known beaches, that have nice fluffy white sand. Some sightseeing/activity on land can be found.
Heading to Aruba early next year for the second time. It doesn't get the rep for great diving like it's sister islands, but there are some nice wrecks with some life in/around them. There is reef, but I don't recall any super fishy areas. It was also drift diving.
Keep in mind the places I say aren't fishy or super fishy doesn't mean there's not life - it's just kind of spread out. For some reason, when I think of fishy, the Georgia Aquarium pops into mind!
