Boo! ;) Just kidding. I'm just popping in to say that you, Mrs. P, are obviously a lovely woman with an irritating problem but you're handling it with intelligence and patience. DannyTN, you've given so much thought to suggestions that might help Mrs. P. I hope one of them will work.
Teens are fascinated with cemetaries. I spent a few nights lurking in them too when I was just a young lady. We never did anything wrong, but I'm sure my girlfriends and I were probably irritating someone living nearby with our giggles, yelps of fright and silliness in general. I'm so glad that folks back then said, "ah, those darn kids are in the cemetary again", but they'd never consider shooting us.
DannyTN came up with so many ideas that I really can't think of any good ones to add. I did think of one that is humorous and just might work though. Teens seem to respect folks who aren't "fuddy duddies" (do they still use that term? LOL) Perhaps you could paint up a big sign to place in front of your house, near the road, that says, "Ghostbusters, please try to be quiet. Respect the living and the dead. SOME of the dead are sleeping in the cemetary, and so are we. Thank you, The Ghost Watchers AND The Spirits who Watch the Ghost Watchers." LOL!