Ringo, I think you are doing the right thing. And if you are in your 50’s, it doesn’t look great to be hanging around a bunch of drunken 19 yr. old girls. I’m sure they are nice kids, but there’s too much room for awkwardness, you know? I’m not trying to be old-fashioned, and I personally wouldn’t have a problem with it, but stuff happens.
Ringo, I agree you are doing the right thing.
Keep him/her at your house over night.Its the right thing to do.
His/her parents ,if they are the kind to be concerned, will wonder where he/she was all night.
If they aren’t concerned it won’t make any difference what you do or say.
That will open the discussion if you decide to voice your opinion.
You probably won’t change his/her behavior.Face it they are teens.Its rebellion.
All you can do is provide a safe place for the kids to crash instead of driving home.
I’d bust him.
Bring his parents into it, and the police if necessary.