I would not agree that "foot passengers" are the last off the ship. That might happen sometimes if you have to tender - those with a tour are tendered first, but not if you are berthed.
Highly recommend the helicopter tour in Kauai - we did the ships tour, but its through Blue Hawaiian Helicopters which you can book yourself directly. The thing about booking some of these tours through the ship - if you have any kind of problem at the port, you are covered. But, on a tour that is simply on a bus (eg Pearl Harbour) its simply not worth it.
We also did the snorkel thing in Maui. That was nice - but again took too long. A one hour snorkel took about five hours - including transportation (bus and boat). Leaves little time to see anything else, or enjoy a beach.