This sounds good, lots more action!
The dump trucks were slow to deliver last year and with the quarry being closer, I'm guessing it may have been a backup at the quarry, packed down dirt or just a new setup.
So if you want more, you will need to figure that in to the time frame, trucks need to be loaded, weighed?, and rolling, don't wait for there buddy to move out together.
I hope the BIG ROCKS just need to be dumped and pushed together and drove over.
Check with the guys running the Obstacle Course, see if there would be a safety factor with two vehicles running at a time, your need twice the help also.