I hear you... but my philosophy is that whenever you're teaching, tools get broken... I keep a necked-down 5/16" end-mill that I personally broke on top of my mill to remind me... we all have had to learn sometime!
but when I've had people over to learn a new skill, I have actually netted more tools left behind than broken in the past... Offered to return them, but it wasn't worth the drive to them for some reason...
If you're not in it for profit (and a host can't be), then loosing a few (inexpensive) tools isn't a problem...
I've sent a PM to some that I know personally from other parties, it's just an idea at this point... maybe it won't go anywhere.