I grew up around more guns than you can imagine. My dad was a big-time collector. And there were two rules:
It's always loaded until you check it
Never point it at anything you don't want a bullet in.
Now there are more rules such as making sure of your target and what's behind it, etc. However, when it comes to guns in the house, those two must be followed. And the nice thing is, they cover each other. Every one has had or will have one AD in their life. But, as long as you remember one of the rules, you'll be ok.
And another thing. I never had to sneak around to see a gun. If I wanted to mess with one, I just had to ask and my dad would get it down for me and let me see it. There was no mystery. And that's the main thing. Take the mystery out of it, teach them the right way to handle a gun and they will be fine.