I never worried about my kids messing with my guns; they are trained in their handling but more importantly know that under no circumstances may they touch one without supervision. Regardless, I have always kept them all locked up tight not because of the kids but because of the kids' friends. You never know which one of them might have a brainless moment and do something without thinking if they ever were to come accross one. Even one second of careless with a gun could cause irrepairable damage; it's just not worth the chance.

In fact when I was a little kid, my teenaged brother's dumbass friend came over with one shell (nobody knew it) and blew off a 30.06 through the basement floor into the dining room table where my sister and I were doing our homework about 10 minutes earlier. Shit happens fast.

I keep mine locked and I'm the only keyholder. You also never know when your spouse is going to go over the edge. (Hey it's in the papers every day; think it couldn't happen to you?)