When we arrived, we already had a reservation, but it did not mention that seats were first come first serve. Honestly, what is the point of having a reservation then?
So the 10:30am departure didn't quite work out. The driver told us that we should sit with 3 kids in one seat, and that was just not happening. But Alison, one of the tour guides, helped us and offered us to wait until the noon departure and assured us there would be seats.
We sat immediately and the tour was quite lovely! For $21 per person (adult) I thought it was reasonable and very fun. The jokes were seriously corny, but it was still a good time. The views were great.