There are about a dozen different threads started on this subject in the last few weeks too. I mention it because there are a lot more men on this site than women and you'll find more variability in the other threads.
I have two boys, ages 4 and 7. We've had firearms in the house long before they came along. They have never known a world without firearms. And because they were taught from Day 1, before they could walk and talk, the rules in this house regarding firearms, they don't have the slightest interest in "finding" the "hidden" firearms.
No mystery, no curiosity.
Both of my boys have been allowed to touch and hold since they were 3 or 4. The older one has been shooting for the last 2 years, and the 4y/o has been behind the trigger twice (at age 3!!!).
Neither of them bat an eye at seeing a firearm. And when tested, they have always passed.
I am not of the "always locked up mindset." I don't think children in the home is synonymous with some big risk of an accident. After one of the big threads on this, I did some digging. The number of children actually injured or killed from firearms (excluding murders and suicide) is ridiculously low. No, I don't make life choices based solely on statistics, but I also don't base them on emotional paranoias either. You know your kids. If you think they all need to be locked up always, then do it.
I ask this questions every time this topic comes up and no one has given me an answer yet: what did families do before there were safes and vaults and trigger locks? Why weren't there massive casualties then? And why do we think we'll have them now if we don't use those things?
Back in the day, of "Annie Oakley", if you will, no matter how many firearms there were in the house, they were ALL loaded, and EASY acess.....