...To the O.P., depending on what type of activities besides snorkeling your spouse likes, I'd recommend Grand Cayman, or for a quiet, laid-back place, Cayman Brac.
I think that Grand Cayman is a great choice for a mix of divers and non-divers. I am not a big fan of the 7 Mile Beach area. It is gorgeous but too developed and expensive for us. We rent a one-bedroom apartment at the Turtle Nest Inn in Bodden Town and the price includes a rental car. The inn is right on the beach (but not the 7MB) and there is very good snorkeling right outside the door. The Inn has an agreement with DNS divers to offer dive services to their guests.
Bodden Town is a more suburban area and it is centrally located with easy access to all sides of the island, but if you want to be close to the shops, restaurants, and attractions then West Bay and the 7MB would be the best choice.
Wherever you stay I suggest a condo or apartment with a kitchen because eating out 3 times a day gets very expensive. We prepare simple breakfast and lunch meals and often go out for dinner - or order a pizza. I also recommend renting a car for at least part of the trip because there is a lot to see and do on GC.
There are some condos and hotels that have a dive op on site and that usually makes things easy but other dive ops will pick you up and that is convenient. Sunshine Suites is a popular venue. You get a kitchenette or apartment and you have access to 7MB and the Westin and I believe that DiveTech will pick you up for your dive excursions.
If you decide to do a 2-tank boat trip in the morning you can also find inexpensive shore dive options for the afternoon that have a dive op on site. Turtle Reef is an example and they charge $15 CI for a tank and weights. We mostly shore dive and snorkel on GC because there are a lot of good options and it is cheaper. But if this is your first trip then you out to see the North Wall and the East End and the Kittiwake and some of the other great boat dive locations.
I have never stayed at the Cobalt Coast resort but they are a small, all-inclusive, diver-dedicated resort. They are north of the 7MB and rather far off the beaten path, you would need a car. There's a small beach but not a lot of beach, mostly ironshore. They offer 2 morning boat dives and unlimited shore dives and snorkeling. Reef Divers is the new onsite dive op. I have dived with them on Brac and Little in the past and they are great and provide valet dive service at no extra charge. But there are plenty of great dive ops on GC.
There is lots of stuff to do on GC but since you will have 10 days you might want to spend a few days on Cayman Brac or Little Cayman just to check it out. Very quiet and peaceful little islands and the diving is even better IMO. But keep in mind that the Wait to Fly rule will impact your diving during an interisland vacation.
Have fun wherever you go!