How else would they have been able to move cars? They didn't go back in reception and ask for keys and description of cars. Plus, wouldn't leaving all the headlights on drain the batteries? I know it is a movie, but this was a goof by director.
shareI wondered this, too. I'm assuming somehow the parking attendants had them?
shareYou always give your keys to the attendant, or else how will they park your car and bring it back?
I agree in this case with such a chaotic group of people moving the cars and a lot of people parked their own cars...yes, that sure is a whopping plot hole.
Soem of the guests did let the kids park their cars but a lot of them just parked on the street and went in.