I spoke with "Gimbel's" (er, DiveBVI) -- and the options just didn't work out for us.

On a whim, I called Blue Water Divers and I spoke with Aja -- Chalk this up to "local knowledge for the win..."
Aja asked me about our proposed "plan A" itinerary.
With this info, she suggested we taxi from CGB to Nanny Cay on our SCUBA day - and not worry about sailing back around.
#bingo

Are taxis always available near CGB dinghy dock? Should we pre-arrange a driver?
Aja said the trip would take ~20 minutes. Anything I should be careful for?