Heck, that's old enough I not to worry about it I'd think. That's old enough (well maybe not the 11 year old, but 13+) to be shown how to handle pyro safely and turned loose.
Of course I'm biased. I was messing with stuff more potent than that, and going squirrel hunting alone by age 13. It was a bit of a different world then I suppose and the fact I'm here now means I'm a self-selected sample.
I do understand erring on the side of chemical safety but not necessarily in trying to make the process foolproof. Mistakes are how we learn. In my experience kids are way more capable than we usually give them credit for, if allowed some leeway to show it.
And thanks for keeping it alive! Awesome stuff, BTW.