What crewed charter company are you with? They should be able to provide a lot of help.
Some crewed charter boats offer diving and at least one crew member is a dive master or instructor. If so, they can help with dive sites. BVI has a lot of dive sites. Selection of dive sites is weather dependent.
There are a lot of choices of duffle bags with frames and wheels. You likely need a bag that does not take up a lot of storage space on board the boat.
Are the costs of clearing into the bvi included?