I am a worst-case scenario type of person. I doubt this would happen at the gathering that the OP is describing but I shake my head internally when I hear parents of HS kids willingly hosting post-prom or Homecoming parties with alcohol who think they have the situation under control because they take the kids’ keys.
You will never be able to anticipate the random incidents that can occur to cause your best laid plans to go awry. E.g., people we knew were hosting a post-prom party and allowing kids to drink (to excess) because all the kids were sleeping over. Well two drunk kids got in a fight and one kid called their parents. Imagine if those parents decided to call the police because they wanted to press assault charges.
In my opinion my personal liability as the host is just too great and I’m not willing to take that chance.