Wow!!!! My longtime partner was a pacifist in theory. She asked that I give up martial arts to respect her convictions. Her precedent was her Dad giving up professional boxing, and for that matter boxing altogether, at her mother's request. Of course, I was always sent outside to face down whatever went bump in the night be it wind, animal, or human.
I did what took to ensure domestic tranquility. Stopped training which I found really relaxing in so many ways and passed my small collection to my father. After the relationship ended, I resumed training and collecting. I changed who I was and altered my outward beliefs for another person. In retrospect, this was a bad idea and not a healthy relationship. I believe your situation is a bit different. I grew up with a gun shop being attached to the house. All in all I guess we got a bit lucky with everyone living and having all their digits. We did have what you could classify as standard operating procedures that helped us along. At 12 or 14 I was scared to death to touch any of the merchandise without permission because of the beating that would ensue. In the modern world one might lose custody of their children for that, I guess? I was trained how to handle these items sharps from 4, and firearms form around age 6. I was allowed to use them unsupervised, sharps from age 8 or 9 (I promptly got stiches from a 3 cm deep puncture when the piece I was carving slipped. I think every member of my family asked, "Do you see now why we never cut back towards ourselves?" I also got spanked somewhere in the process), firearms from 13 or 14 to hunt small game. These last three items are somewhere between out of vogue to criminal offences now, but they kept children safe for millennia.
These aren't answers, more in the line of data points for you and/or commiseration. I am glad your son's friend is ok. Boys (children) get hurt. The pain experienced as a child helps harden us up for what will happen as an adult and teach us as well. The burned hand.... Have you ever thought about how many children had to burn their hand to make that a colloquialism?
I've worked a lot of tough and dangerous jobs and without those childhood experiences I would not have had the knowledge to get those jobs or survived very long. They will both be more cautious and wiser in the future. Knowing that there are pitfalls and consequences to our actions. That is a good thing. A silver lining to an unfortunate event. Good luck in whatever course you choose.