I go old school on the charcoal. When grandkids want to shoot, they love to see reactive targets. I've been using a couple of T posts in front of the berm with wire between them, some string and a rubber band tied to the string around the charcoal to hold it. Requires a few rubber band changes though.would be easy to make/design for a 3d printer. not a bad idea. :-)
They aren't concerned with clover shaped groups on paper. Turning the briquettes into dust works for them.