Someone else said it, but I will reiterate the point: put in a motion-detection camera and file a report. You will want to rebuild because that's just the way we humans are and I think that's easier to do when you feel like you can protect yourself. A picture is worth a thousand words, as they say. For this instance, a gun would have done you no good. You are going to shoot at kids? Not in this day and age. Get a picture. It's way more powerful.
I would also consider the point that all this happened and no one in your house heard a thing. Your barn is either quite a ways away or in an auditory dead zone. Perhaps you might consider hooking a buzzer up to your barn doors that sound off in the house when they are opened. Doesn't need to make a sound out in the barn, but it would give you an auditory clue in the house that someone is opening those doors.
Just my thoughts...