I am assuming you are coming by boat.
The process is something like this.
Clear your vessel out of the BVI and check in to US C&I - can be done in Cruz Bay STJ or in Charlotte Amalie STT.
The absolute shortest boat trip on your part is to pick up a mooring off Cruz Bay STJ and have your guests take a taxi to the ferry from the airport and then pick them up when they land in STJ.
If you want to take your vessel all the way down to Charlotte Amalie you could anchor right by the airport in Lindberg Bay and pick them up by dinghy or get a slip at Crown Bay and have them meet you there. There are a few other anchoring options but none closer.
After they are on board you can proceed back to the BVI and clear in with their names on the manifest.
If you must drop them off in the USVI at the end of the week you must again clear out of the BVI and into the USVI - once again dropping them in Cruz bay STJ is the easiest and shortest trip for your vessel but the other info is about the same depending on how close you want to drop them to the airport.