Just found direct flights from Charlotte to Sint Maarten.
Either of you ever been?
Haven't dove it; visited a few times on cruise ship stops. A few thoughts...
1.) Though rarely the subject of 1st hand trip reports as a primary dive destinations, what reports I see tend to be good, with Caribbean reef sharks often seen.
2.) It looks hot, sunny and arid, but more richly vegetated than Bonaire, and somewhat mountainous. There are beautiful beaches and the sea around this island can be gorgeous.
3.) It's a high frequency cruise ship port, so it's got plenty of topside excursions to entertain people. I've been on some of these.
4.) At least when I read of it many years ago, it was seen as something of a '2nd place after St. Thomas' as a Caribbean shopping destination, so if you've got shoppers in tow, they can probably entertain themselves. If they're doing it on your dime, maybe that's not good...
5.) The political divide into French and Dutch sections is real. I was told a phone call from the French section to the Dutch section is long distance, but to mainland France is a local call.
6.) At least as a cruise ship passenger, where we ported at the Dutch part, it seemed like English was no problem. I don't know how widely spoken English is in the French half; never had a problem as a cruise ship excursion goer, but then consider we wouldn't be off the beaten path.
7.) I haven't heard either way on costs, but at least I haven't heard the reputation for being expensive that seems consistently reported about Grand Cayman and Providenciales.
8.) The diving I did out of Provo. tended deep overall, and I didn't get the impression Provo. had as much going on topside as St. Maarten does in terms of official excursions.
It really gets down to what your crew likes to do. If I weren't going via live-aboard, I'd pick St. Maarten over Providenciales in a heart beat.
Note: Somebody may mention Saba is close to St. Maarten. I don't know if they're taking tourists now, or whether you're ready for that level of rustic, plus they're known for pinnacle diving, which IIRC from reading (haven't been), can be deep.