We (2 of us) really wanted to do it last May when we stayed on VG for 4 nights. I touched base with Gumption and the Necker scheduling team way ahead of time and they had us on the list for two different days. For whatever reason he didn't have enough people to fill the boat for a Necker tour, so we didn't get to go. Sounds like the OP has enough with his crew, so it won't be an issue, but just a heads up for anyone else that it is subject to a minimum number of people.

Felix (kris)