This is less than an answer, but more than a comment…
A large percentage of your travel budget will be spent on the cruise itself, given that it includes lodging, food, and transportation. As it appears you don't have your heart set on seeing a particular part of the Caribbean, the next important question is: what is your "cruising style"?
I've been on three cruise lines: Holland America, Royal Caribbean, and Norwegian. I'd go on another cruise in a heartbeat on one of them—because it fits the sort of traveling my husband and I like to do. If you like to dress up and eat high-end food, the cruise line you want isn't the one that caters to honeymooners on a tight budget or to families with small kids. If you like things to be super-flexible, you don't want the cruise line that assigns you a nightly dining reservation at their one restaurant. And so on…
If you like upscale, be aware that all cruise lines put their best efforts into their longer cruises. I've been on cruises ranging from 4-14 nights, and the experience (and amenities!) pretty closely tracked with the trip length.
Once you've figured out what cruise line and trip length work for you, there are likely to only be a few options left. Take whichever of them works best—there really are no bad Caribbean trips (so long as the weather cooperates, of course).