My 8-year old knows I carry as often as I possibly can, and he knows that we need to be discrete about it. One of his friends at school once said to us that his Dad had a gun in his truck, and my son looked at me, but said nothing. I was armed at the time, and my son knew it. I only worry about this son outing me a little bit, because he likes to come up and give me a hug from time to time, and I'm afraid he might inadvertantly expose my weapon when he does so. (But I'm glad he still likes to give me hugs, and I'll cherish that for as long as I can, because I know it won't last forever!)
My 3-year old is a different story. He is incapable of discretion at his age. I try not to dress with him in the room. Still one morning, as I came out of the bedroom, he asked me, "Where is your gun, Daddy?" I had my P3AT in my pocket, but I told him that my guns were put away. He knows that I have several guns, and that I will carry them around the house, but I don't think he knows that I carry them outside the house, yet. Or maybe I'm underestimating him...
At home my guns are kept in a safe, on me, or out of reach of the 3-year old in a locked room. The 8-year old knows not to touch the guns without my making sure they are safe first. Both of my sons know that they can look at and touch (and even pull the trigger on) any of my firearms that they want to, so long as I make sure it is safe, first. I have done the leave a gun (unloaded, no ammo anywhere nearby) out test on the older son a few times over the last few years. Unfortunately, he failed the first time and just picked it up. He has not since. He is now my range buddy. It is about time to start teaching gun safety to the 3-year old.
Remember, in a life-or-death situation, when seconds count, the police are only minutes away.