You're probably overthinking this a bit. The easiest and most cost effective is the 10 minute taxi ride from STT to Charlotte Amalie ferry dock and take the ferry from there to Road Town, Tortola and it will be a 15 minute taxi from there to CGB. Not sure why you would go from Red Hook since that's a 40 minute taxi from STT..... this will be a shorter trip. Happy to provide the name of a taxi company and driver on both ends who will make sure to get them where they need to be but again, it's not complicated.... no reason to escort them unless you're already in STT going to BVI. If you want to triple your cost and take a water taxi, be aware that it's a long taxi trip to Red Hook and if it's raining, you will likely have a delay in departing on the water taxi or get wet crossing. Having done both, I've found the water taxi to be no more efficient or time saving - I'd always opt for the larger ferry.