Are your handlebars actually bent - or did the shifter just twist a bit on the bars? The shifter isn't actually a part of the bar, so it can rotate, in fact if the person who installed them was savvy they didn't crank down too hard on them as it is better for the shifter to twist in a fall - then it doesn't break the shifter or the handlebars and you can just rotate it back into place.

As far as the kid goes - don't beat yourself up too much. You gave him ample warning and he sounds quite old enough to have been in control of himself.