B.B.
We had my son's first birthday party at the lake. I rented out a pavillion, but there was still a fee per car to enter the park. I don't know if it was PC or not, but I just put a small footnote on the invite (they were the print it yourself kind, not the fill in the blank) the amount per car. It was our family and close friends, so I knew they wouldn't care if it was "proper etiquette" or not. We had already paid for all the food, the pavillion fee, and decorations, so we didn't have the money to pay for everyone's vehicles. They all understood and were just happy to be part of my son's big day!