I'll bring mine. It's a 5-gallon cooler with a spigot, and I've made a reflectix "coozy" for it. It worked last year very well in the car. After filling it at the Ranger's station with the hottest water from the tap, it was still warm 24 hours later. Maybe we can take a tarp and make an enclosure in the pavillion for it which will keep the wind off, which should mimic the environment of the car. Also, I think if we had another cooler or 2 it would be better for the size of the group.
Thanks for posting, Doctari! And, please, please find someone who will trade hours with you so you can go!.