Glad they were caught, I'd probably have them do community service like wear signs around their necks for the next 50 weekends (especially nights) saying they were caught breaking into vehicles of people who support the NH economy. (or that they are just @$$h01e$)
Go the public embarrassment route in their cliques & the schools next year. At school because there are a handful of 14 & 15 year olds thinking, "boy how dumb, they got caught" They'll have their drivers licenses soon with nothing to do, out late, with a couple of friends & beers. How many square miles of playground & just a couple of cops. Taking stuff was their downfall. (Once I wasn't the choir boy I am now - before many of you were born of course.)
How do you prevent it? Ban all alcohol, curfews, leave crap (literally) in your car. (Hard to do that)
Some trailheads with good site lines at night are good targets because the cops don't drive without lights (Appalachia, 19 Mile) are easy, in & out accees loaded with cars most nights. Parking at PNVC & C-Notch at the H-C would helps as their is a lot of lights & activity. Park on the side of Lafayette Place when overnighting in the notch because access isn't as good & more activity & better site lines from the road.
I'd have more but I've forgotten more about this type of behavior than these kids know. (Rule one, don't get caught if you think being your cell mates wife is better than being released to your Dad. - no way was I getting caught, but back before cells, & GPS, it was easier)