Hi MW1957,
I was so worried about that whole 'no good deed goes unpunished' thing. It's happened to me (non ipad related.)
And I almost brought it up and was thinking that the owners could be nuts, violent, etc., but I thought the better of the owners and hoped they would be grateful and not be so stupid and selfish not to realize that the ipad was somehow lost by them, most likely from their car and I figured you'd leave it at the office so they could pick it up at a neutral location for your protection.
How stupid of them to not have thought that their smashed ipad was lost by them. Most who steal ipads these days are smart enough to turn off 'find my iphone' and reset the ipad. Then many get on these forums asking for help deleting the previous owner's ID and set it up as new.
If I were you I would print out this entire thread and carry it with you everywhere you go. And some day if your sons point them out, and if they don't look like losers who enjoy the thought of confrontation, you can hand them the printed copy of all this, say 'you're welcome' and walk away. Who knows? It could be a parent at your sons' school and they'd know that you know they don't come from a place of kindness. And if they have any sense at all, they would at least have enough dignity to apologize and thank you.
And no matter what, you're right - your sons learned a good lesson about doing the right thing, and I think we all learned that we must approach doing the right thing with caution, especially when you're not with your kids because at their ages they still won't always 'get it' when they mean well.
Congratulations, though. You did a good thing!