I have four kids, all grown, but all were raised with guns accessible.
Since you can't actually child-proof a gun, the only alternative is to gun-proof the child. Those too young to comprehend are kept out of the loop. Those old enough to understand are shown, graphically, what guns are capable of. (Blowing up a cantaloupe is a good way to get their attention, tell them to pretend it's their head, then let fly. They WILL remember that!)
Beat the safety rules into them from the time they understand language. It pays off.
Teach them all guns are always loaded, unless a grownup clears them. In time they become responsible enough to do it themselves.
Let them handle, manipulate and dry-fire any gun they can. It removes the "Forbidden Fruit" aspect. I let my kids handle any gun, any time (within reason), and made them show me the safety features, and the proper method of opening/checking/clearing each weapon. My kids took great pride in knowing how.
Once they've demonstrated that they can safely handle the weapons and understand the safety rules (ESPECIALLY Muzzle awareness!) take them shooting. Once they see how the guns feel and react, they understand even better. The one rule I beat into my kids from day one was No Touching The Trigger Until The Sights Are On Target. If they follow that one all the time, there is a lot less to worrry about!
Shooting is a great family activity. It teaches responsibility, safety, and independence, among other things. Enjoy those little kids......in about twenty minutes they'll be asking to borrow the car...........
Papajohn