Guns in the home, safety

We own a handgun which my husband stores unloaded in a locked case, separate from locked ammo. He's a soldier so I trust how he stores the weapon but with kiddo #1 on the way I am getting more nervous about the long term. Can anyone share advice about raising kids in a home with a gun? What do you tell them, at what ages? What about if grandparents or friends own guns, what do you say to them about storage etc when you bring your kid over? Yes, we live in Texas. And no, I am not pro-gun, I'd be happy without but due to my husbands line of work I am fine with him owning a weapon, which he fires responsibly at a range only.