While you don't really seem interested in CUN, DL just cancelled their scheduled RDU-CUN flights for the winter this past weekend when they added the BOS Caribbean flights. It was supposed to start in November and run as daily throughout the winter. A connection in ATL is going to be required if you want to go somewhere in the Caribbean on DL. You can use Google Flights to search for destinations by using ATL as origin and Caribbean as destination and selecting non-stop, Skyteam flight options. SKB, ANU, and BON look to be among the Saturday only options.