I like Cayman a lot. But while it's certainly possible to do nice shallow dives there, it's not the main draw and focus of the place and arranging that for all your dives could prove difficult/limiting. If you really want to stay shallow for now I'd suggest saving Cayman for another trip.
I think Curacao is a good option for your situation - easy to stick to shallow depths, lots for your wife to do, easy boat dives, and beaches where she could hang out while you do a shore dive if you are ready to set out on your own. There is a huge variety of accommodations, so it depends on your budget, what sort of place you'd like to stay, and what you wife wants to do and how convenient you want it be? Are you more interested in boat or shore diving?
My suggestion in Curacao would the Marriott Beach Resort by Piscadera Bay. I think it's a good all around compromise on everything for the island, not in town but close enough so it's not a long drive to lots of shopping/restaurants/sightseeing, also a couple other hotels and restaurants in walking distance. Nice beach/pool/resort facilities. I stayed there for a night once but didn't dive with them, but the dive shop has a good rep, they've got some kind of on site shore dive, and their boat has never looked crowded when I've seen it. From what I've seen and heard, I'd skip the Hilton next door. Floris Suites across the street is very nice, but not on the beach and has more of a business than vacation vibe - the Curacao convention center is nearby. There's also some condo/apartment places around there if you want something like that rather than a resort.
There is a variety of nice/interesting places to stay in town. Renaissance, Scuba Lodge, Avila Beach are the first to come to mind that I would consider myself, but I don't because I'd rather be away from all that, and it's generally less convenient to dive heavily from a downtown type hotel. But it gives the option of walking to a lot of stuff, and you can get picked up for diving, Bas Harts or Dive Bus come to mind.
You could also look at Lions Dive, Seaquarium Resort, or Seascape AI, all near each other on the other side of town from the Marriott but also not too far, Onsite dive shops and maybe shore diving, and lots to do right around there including the Aquarium. Too busy for me and not my favorite area of the island to dive, but if you prefer that atmosphere you might like it.
I like Kura Hulanda Lodge. Go West diving there is a good shop and there's good shore diving on site. But it's a long way from much of anything so restaurant choices are limited. And not a lot for your wife to do unless she's happy mostly by the pool and beach, talking walks, and maybe could arrange a massage. They at least used to have a shuttle to downtown, it did not run great hours if you were diving or to eat dinner in town, but fine for a non-diver to do a sightseeing/shopping junket or maybe hit the spa at the sister property downtown. You could even consider splitting a trip between the 2 Kura Hulandas to get a bit of both.
There's also a bunch of resorts further east (Jan Thiel/Spanish Water area) which I don't know a lot about, but while you could arrange diving it doesn't strike me as the area to base yourself if that is one of your main interests.
The Curacao ostrich farm could be a fun family daytrip for a non diving day, maybe your last day. It's way out in the boonies to the northeast. There's a good restaurant there, and a nice gift shop with some different stuff.