Welcome to the world of RV Park logistics. No matter what the policy was/is there will be upset people. It's hard enough to get multiple families to make time and agree to meet at the same place. Obviously, they usually want to be next to each other. With a strict first come/first served policy, that probably isn't going to happen. The end result would either be the park loses those 8 reservations (they will go someplace that will let them be together) or they will all arrive and be upset. Waiver at all on first come/first served and you get upset people like the OP.
If someone has a solution that will work for everyone, all the time, I will be glad to steal it and claim it as my own.
