It all turned out for the best, however. If I had had time to arrive earlier and assemble with the crowd down beneath the lighthouse, I would have missed the largeness of the moon; my 600mm lens being way too long to fit the lighthouse and the moon into one frame, necessitating my having to back off on the zoom, and what I would have ended up with (and did, when I finally found my way over to the lighthouse after getting my emergency and impromptu shot from the causeway) would not have been much different than many of my other moon/lighthouse shots in the past. Distance and landscape and context were my friends in this case.
This is not exactly what I expected, or had planned on, but it will suffice as a learning experience.
Now, what time does this thing set?