I wouldn't let him go over there.
I understand that you trust him, but can you trust the others with your son?
Smoking, alcohol and maybe drugs?
But, alcohol alone could easily cause more then enough trouble.
Then the pressure of the other teens.
Here try this, try that. Don't be so silly do what we do... Try to smoke, drink this, etc.
It's dangerous and maybe he might think it's childish to stay at home. But in reality it's far more grown up to stay miles away from such parties.
If he'd go to a night club then there's also security over there and other staff that do keep an eye on things and jump in when things are getting out of hand.
Here is only a group or drunk teenagers. No one to keep an eye on things. When things do get out of hand it'll be difficult to get out of there or to stand up for yourself and tell them:
'I don't do this or that'.
It's not that he's a teenager, even for an adult to be at such a party is a recipe for disaster. Things might go well, but if they don't.....
It could get really ugly, really quickly.