Yeah, I have a safe, but it's not to keep him out, but the neighbors. I went the route that is suggested by a number of the gun-owning authorities (as opposed to DiFi, BabyBoxer, and L(amebrain) Tolley), I taught my son how to shoot. I won't say how old he is, but just suffice it to say that he isn't interested in the opposite sex yet (hence, he won't need the rubbers previously mentioned for a while!).
The philosophy presented was that if they do not have the curiousity then they won't try to break into your safe and play with them. So far, it seems to have worked. My son has some interest in getting better scores when he shoots, as a goal, but his curiousity has waned.
He goes twice a month to a Jr. NRA shooting class, and is about 3rd youngest in there at this time. I'll note that from the information we have, NONE of the school shooters has been a part of an organized training session on guns, EVER. That's Eddie Eagle, Jr. NRA, whatever.
Finally, my wife and I pay attention to him. We jointly take part in providing him a stable home life, and a reasonable amount of interaction. While I doubt he'll be the next 16 year old Olympic class shooter, he is interested in politics, and Chuck Heston may have a replacement by the time he finally decides to retire.