His parents prob don't even know/care about him driving drunk....Hubby wants to talk to his parents
Talk to the parents. This is their job. If they care about their kid, they'll get involved. If they don't, put your local police on speed dial and get them involved the second the whippersnapper steps out of line again. If you were able to positively ID the kid that fateful night, and especially if your husband could, too, then take a few minutes and go down to the appropriate police station and file a report/complaint. They may not be able to take any action to your satisfaction at the moment but it will start a file on the kid and establish a precedent. Any future complaints will be added to this file and when he gets enough, even if he has managed to avoid actual arrest up to that point, he will be identified as a "Nuisance" by the cops. They WILL be able to take action at that point, either against the kid or the parents, and no matter what happens, you'll have a paper trail that backs you up so you don't come off looking like a nuisance, yourself, to the hard working local law enforcement. I've had stalkers, I know how this works. Good luck.
PS: I just visualized you guys keeping your garden hose charged and ready in the front yard so you can run out and blast him in the face if he trespasses again. Works on cats.