I have no idea. I can say I don't recall hearing of any gun crimes committed by children anywhere near here, although I don't pay any real attention to what goes on in the cities. There are some pretty warped irresponsible people all over though, and they're dangerous regardless of whether or not they have guns, and regardless of what the laws are. Around here, MOST houses have guns inside. And the doors aren't locked. And we leave the keys in the car when we go inside. The "bad' kids are the ones who drive around with baseball bats and swat at mailboxes, or throw toilet paper in peoples yards.
There are many, many ways that even as gun handlers/owners they're more likely to get in trouble with, get hurt by or with, etc. I'm more worried about my kids driving, fishing, riding the school bus, working with my power tools, or playing sports than I am about them shooting. In the end, it's the behavior of the individual that's the deciding factor, not what they have in their hand. And laws won't stop "bad" people from behaving badly.
As for me, I try to keep my firearms put away, but not necessarily locked away. I teach my kids how to use guns safely and responsibly, and the "rules" that go along with that. But more importantly, I teach them some pretty basic rules about how to be a responsible, respectable person, and about being safety conscious in general. I can honestly say that as a parent the things I'm teaching my kids about guns have very little to do with the legal aspects. A law-related thing I'd teach would be a situation where responsible handling might also/still be illegal. An example of that might be packing a firearm away in the vehicle for travel, where it could actually be violating the concealed carry laws. Sometimes it may actually be safer to violate that law though- for example, if you have a firearm, unloaded, in a case, and need to run into the store or gas station, it may be best to slide it under the seat so it isn't visible. In general, though, if they act responsibly they won't have any problems with the laws.
I can't be around my kids all the time, so they need to be taught what's acceptable and what isn't so when confronted with life they can (hopefully) make decent decisions. No quarantee of course, but that's all you can do in the end...