re: I had a top day with one of the grandsons in the shed during the recent school holidays.

Well I can relate to not stretching kids from my sons Scout days when they couldn't use matches or pocket knives.
I am not sure how old the grandson is but assume High school age.
That being the case there is no reason to not "trade or competency  test" them under supervision if they have the shills and interest to learn.
Lets learn under a training situation rather than  in "combat" so to speak.
For Example
 I learnt to drive an APC in the transport yard doing FWD and REV maneuvering and at that stage I think I only had a motorcycle licence.

I took my son canyoning at a familiar spot in the Blue mountains at an early age.