Belize would make my list also.
The two liveaboards (Belize Aggressor/Sun Dancer) leave from Belize City which is where the intl' airport is. I'm pretty sure both pick you up there. After you return either fly/ferry over to Ambergris or fly south to Dangriga/Placencia - from there many of the non-dive Belize attractions are accessible. Ambergris is a little isolated by geography. So are the atoll resorts, many only offer once/twice a week transfers so you'd have no chance to see the land-based attractions. Like:
Vacation Activities in Unique, Unspoiled Belize | TravelBelize.org
Splash Dive in Placencia is who my friends used. If you can time it right this spring, you can dive with Whale Sharks off Gladden Spit. Splash also can set up a lot of the non-dive inland activities. Hamanasi is another option if you really want to make it up to her. If you really, really
have to, Turtle Inn - that Coppola place nearby...
The problem with splitting destinations outside of the ABC islands is that a lot of connections only route back thru either Miami, Houston or Dallas so you burn two days getting between Caribbean destinations that are barely hundreds of miles apart.
Other possibiliities for combo LOB/island trips are Turks/Caicos (Aggressor or Explorer), Grand Cayman(Aggressor) or Roatan/Utila. You could even do the MV/Pearl out of Utila then fly over to Belize for the 2nd week. Tropic Air in Belize flies to Roatan/San Pedro Sula. Both are connecting points for flights to/from Utila. Or stay on Roatan. All are not as good from the non-dive perspective though.
The Turks/Caicos boats are currently off the Dominican Republic doing whale snorkeling till next month. And when they return, the best of what they dive can also be accessed via day boat from Provo so that seems redundant. Not a lot of cultural stuff on Provo but a lot of exceedingly nice beaches. Grand Turk is smaller, just a few resorts but the cruise port is there.
Cayman Aggressor might hit all three islands this time of year, weather permitting but Grand Cayman (port) is light on other cultural activities. And the Sister Islands are really light on everything but good diving. Not that I'm faulting that, Little Cayman is some of the best diving in the Caribbean from what I've read.