My wife is a non-diver so I need someplace where there will be something for her to do.
This being either on site on in very close proximity.
Not sure what you have in mind for something for her to do, but if it's just requiring a beach or pool, then that's possible. Also don't know of any resort/hotel that runs a boat from their property so, close proximity will be your option. Most ops, at least on the west side (Frederiksted), will have you back by 12:30. As I recall some dives I did out of Salt Bay got us back just slightly later, but the drive back to where we were staying was another ~30 minutes.
I have only stayed in the Pink Condos in my trips to St. Croix. Some are available through Airbnb and they are less than a 5 minute drive to Frederiksted. There is a nice, practically private, beach and it is a great snorkeling spot. Being on the west side, you can watch the sunset.
Great dive ops are in Frederiksted - I'm partial to Nep2une Scuba which is located right by the Frederiksted Pier, which has to be one of your dives (can be a shore dive day and night.) There are a few places to stay in town,
Places to Stay In & Around Frederiksted – Nep2une Scuba but there wouldn't be a lot for your wife to do except maybe hit a beach somewhere.
Christiansted has places to stay, but again it's not like the resorts/hotels have a ton to do. Some, such as the Buccaneer may have a beach with water activities and/or a fitness center. The Buccaneer has tennis and golf. S.C.U.B.A. (St. Croix Ultimate Bluewater Adventures) has a boat that leaves from the pier right in town across from Hotel Caravelle (they also have a boat that leaves from Frederiksted.) Christiansted is the more touristy area and where people go to shop (and eat/party.) If you stay close enough to town, your wife could walk along the boardwalk and hit some of the shops.
Divi Carina is located on the SE side of the island. They may have pickleball and they do have a casino. You would have to drive to Frederiksted or Christiansted for the diving though.
As far as diving, I'm more partial to diving on the west side (Frederiksted.) There are some wrecks, coral, and the Pier. Boat rides are shorter and the water is generally calmer on this side. The north side (Cane Bay, Salt River Bay) has walls, canyons, and some neat topography.
There used to be a SB member who lived in St. Croix. Maybe he will chime in with some more info.