The marina charge does not normally seem to vary with length or beam for the size of a typical charter boat. I have no idea about the generator use at the dock, except to state that I would not run a generator in that circumstance.

Warren S/V Scuba Doo
Lagoon 50 (winner of best crewed yacht under 55 feet at the St. Thomas crewed yacht boat show).

https://www.cyabrochure.com/ebn/2307/pdyrX/6642/4///