Ouch.
I agree there's a lesson to be taught here. Maybe let a luthier handle the work instead of doing it yourself, and let the kids pick up the tab out of their gig proceeds.
^This. No accountability and no consequences is the problem imo. I was raised and taught that if you were ever loaned anything, you treated it better than your own, and simply replaced it without asking if you damaged it. It was simply a matter of responsibility. Seems to be the opposite attitude these days, as in...it's not mine so why should I care? I just see it all the time now. Fortunately there was no serious/permanent damage in this case.