Are you restricting this solicitation to the Caribbean?
The best diving (quality) while keeping in mind the per tank or all inclusive basis is in the Philippines or Red Sea (Egypt).
I’d suggest Puerto Galera in the Philippines based on what you’ve told me about your wife. Concierge diving at its best. I showed up for every dive with computer and mask and the rest was done for me. I stepped off the boat and deck hands were waiting to analyze nitrox; I only needed to sign and watch. My gear and tank was on the boat for every dive, including my camera, just as I like it. I walked off with the same gear I went on with. Next dive, they lay my wetsuit and boots, socks or for me to put on. I ordered my meal before departing for the dive and it would be almost ready by my return. They rinsed my gear and dried it before departure. The only thing I carried all week was my mask and computer. They take care of everything else.
#spoiled
A full week with nitrox, 4 dives a day on a boat with a DM or instructor, ocean view room, private round trip transfers, all meals....$1200 at Asia Divers/El Galleon which some people will tell you is a “premium” aka on the expensive side. I happily pay it for the dock and it was so worth it to me. It’s a top notch op.
it was like a liveaboard.
Should you want to a la carte it, you can get nitrox dives for $25-30 a tank on a boat with a DM, possibly with equipment rental as well.
Another one you should look at is the Red Sea out of Egypt. Land based diving and liveaboards are very affordable. 3 tanks on a boat with a DM with lunch for $50, easily. You could probably package a dive arrangement quite cheaply. To give you an idea, including taxes per night at the Marriott in Hurghada, we are paying $120 a night for 2 adults in an ocean view room which includes breakfast and dinner. (We opted out of lunch since we would be diving). You can opt be on a luxury dive yacht liveaboard for about $1200-1300 a week with free nitrox. Lots of options.
The flight to Egypt is more expensive than the flight to the Philippines for us but I know there are always deals to Asia from Texas. It’s obviously more time but it’s often same price to fly to Caribbean or out to Asia so the decision is always easy for me, given the quality of the diving. The only thing is it’s a larger time commitment but your landing costs (eating/diving/lodging) are substantially lower than the Caribbean.