I have three daughters: 6,4, and 1. As a gun owner, I recognize that gun safety starts with me. Teaching my children about firearm safety is extremely important, as I am human and prone to mistakes. My personal rule for my house is that firearms are either carried on-body or secured. We have routines that are strictly follow to avoid situations where the education will be needed. Education will protect my children at my home and others.
My daughters are free to ask me any question about my firearm or other peoples'. I have offered to let the older ones handle my firearms, with supervision. They ask questions about different pieces and parts. I do this to take the curiosity element away. They know that there is absolutely no reason to try to sneak a peak, they just need to ask. ( or agree when Dad offers)
I would expect my father-in-law (who carries) to get explicit permission to teach my children about firearms, take them to a gun store to view firearms, or when they are older, a range. Not just because of the subject matter, but because of my responsibility as a parent. You and your son may have differing philosophies and ideas. It's important for children to hear a consistent message and their role models to be in agreement.
My two cents.
Also, the NRA offers some resources for children:
https://eddieeagle.nra.org/