BVI to USVI Customs question

The procedures and time involved for your group, particularly as all are US citizens, is not too great; particularly when offset against a 10 day cruise. I will assume that your charter company will allow a trip across to the USVI. You will need your boat papers from them and then will need to clear out in BVI; Road harbour is a bit of a hassle as you need to get to the Ferry Terminal and they don't have a dinghy dock. The West End, being within sight of the USVI is the logical choice but you can also check out of Jost Van Dyke or Virgin Gorda. I would recommend checking in to the USA on St. John, there is a draft restricted temporary anchoring area in Cruz Bay (too shallow for my deep draft) or you can take a mooring ball somewhat north of Cruz Bay in Caneel Bay and dinghy in to Customs & Immigration from there.
I would guesstimate about 30-60 minutes to check out at the West End (assuming you time it well and don't check out when a ferry arrives) and about the same time in the US. I normally need to ask for checkout papers in the USVI (they aren't issued as a matter of course) but when travelling to BVI they will let you check in without checkout papers. I am not sure what the checkout procedure for you would be, as a non US-citizen I need to go into the offices but in your case a telephone call might suffice. Checkin into the BVI will take about 60 minutes.

I went to St. Johns the first time to pick up and later to drop off a friend. After dropping her off I had intended on sailing back the BVI but ended up spending a week in and around St. Johns, mostly moored in Caneel Bay, and loved it. The food at the campsite is worth the 200+ steps that you have to surmount and those steps help to work up an appetite as well.

I just didn't want to frighten the OP away from fishing. I do think that the stories I heard weren't charter boats with guests not having paid for fishing permits but private vessel where the BVI authorities had (previous) issues with. And the one story from early this year, where the boat was at first impounded and then levied with thousands of dollars of fees and fines, seems to be a lot more involved than the initial reports of some poor US boater having his boat confiscated because he hung out a fishing line - meaning there are certainly always 2 sides to a news story.

Back to customs - I know that US customs & immigration requires all people on board to present themselves when a "furriner" is on board, but wasn't sure if that applied to boats with only US citizens aboard as well.

I've checked into and out of the BVI many times, and have never had significant delays but have heard of cases where the process can take excessively long - perhaps I've just been lucky. Immigration in St. Johns and St. Thomas was always fast, efficient and exceedingly polite or even downright friendly (note I never said the same about the BVI ).