Interesting question. We only have one child - a boy who is now 11. I haven't talked it over with him but this is what I'm thinking:
There are a few guns in my collection that have been in the family for generations. He will most definitely inherit those guns.
There are a couple guns in my collection that are my son's guns (meaning, I bought them for him). He is welcome to take them with him when he moves away from home as long as he is able to store them safely and securely.
The rest of my guns may be kept or sold, at my son's option, upon my death. I don't plan any sort of mass sell-off prior to that time.