If family members want to give you money toward your cruise as OBC, I would advise they call RCCL direct and have them add the amount directly as OBC. Any unused amount can then be credited to your card on file or in cash. Of course, those adding this OBC will need to have your reservation number, I think. If they to a gift card, any unused amount will go back to the gift card and can only be used, onboard, on a future cruise.