When I hear "condo" and "include a truck", my mind automatically jumps to Bonaire. But that's really not a great option for a non-diver, as there isn't much to do other than dive.
St. Lucia is a beautiful island with plenty of land activities in addition to some decent diving (at the southwest end of the island). Not sure about the condo scene, but if you can find something that would be a great option.
I haven't been there, but I hear good things about Curacao - apparently better beaches and night life than Bonaire. I checked into VRBO places about a year ago, and there were a lot of good options. Should be plenty warm in December that far south.
Grand Cayman might also be a good option to check out. I stayed on Cayman Brac a few years ago and really enjoyed it...but stick to Grand Cayman, because Brac is tiny, so not much else to do other than dive (unless your wife is into caves and rock climbing).
James