I was raised in a house that kept an unsecured shotgun in the parent's closet all the time. I was never instructed on how to use it, just that I should never touch it. I never did touch that gun until just a few years ago in my mid 20's when I got my dad out to the trap range.
My grandpa did teach me a bit about shooting when I was 8-9 years old, but there wasn't much emphasis on safety. No eye protection, hearing protection, and no talk about the 3 (or 4) rules of safety.
Sometimes I'm amazed that nobody in my family has had an ND that resulted in the death of somebody or something. Grandpa almost killed a cat once when "cleaning" a muzzle loader I hear.
As far as locking up the guns or putting a lock on the gun: Gun vaults, steel cabinets, etc. will be what I employ for HD guns whenever I get around to having kids.
Trigger locks are just stupid. Brain dead stupid. What's rule #2 again? Never put your finger on the trigger unless you're ready to fire. Why on God's green earth would anybody stick a metal rod right in front of the trigger and lock it there?
In Ted Nugent's book, God, Guns and Rock & Roll he related a story about an ND in his own house. One of his gun racks was set on the floor, rifles were mounted muzzle up, and they put a cable through the trigger guards of all the guns. Sure enough, one was left loaded and his toddler pulled on the cable causing a discharge. Putting anything inside the trigger guard of a gun is just stupid. We repeat this over and over to ourselves but sometimes ignore it when it comes to anything but out fingers.
I will never understand that.
When I first got into firearms the man (Marine) that got me on this path once explained what he does: On every floor of his house there is a gun vault. When the kids go to bed he opens them up, loaded pistol ready and waiting. When he, or his wife I guess, gets up they lock the vaults and they're good to go.
And yes, he did gun-proof his kids. They were well schooled on them. When I went to the range with him and his 12 year old he asked his kid if he'd be OK with shooting the 9mm for that trip. The kid's response? "I have no parabellum with that!" Yeah, I'd say that kid knew his guns pretty well.