You cannot reasonably justify a minor who has had experience shooting real steel to be safe with airsoft because they are completely different things.
Everybody knows that a real steel rifle has the capability of killing people. Thus, unless you had a mental condition, any person would exercise extreme caution handling one. We all watch the movies, we all know what a (real) gun is capable of. Hell, even under the most sterile conditions with nobody around for miles, I'm still afraid of pulling the trigger. Minor or adult: this respect of "objects capable of killing easily" is embedded in each and everyone of us.
Whereas with airsoft - the things shoot plastic balls for fuck sakes. In the eyes of the misinformed, it is treated as a toy whether we like it or not. When an object is treated like a toy, any respect of it is thrown out the door and that explains why kids feel like bringing them out to parks and such. Unless our guns have the ability to seriously (and easily, don't try debating this) harm or kill people, they will be generally viewed and used as toys. Hell, even people actively on this forum (with all the safety rules and practices known) handle airsoft guns like toys.
So, no. Just, no. Your child is not qualified to (or should) be handing airsoft guns just because they have experience safely shooting real guns. They are different things entirely.
Age Verifier - Unionville and Markham.