One thing that I have not seen mentioned here is practice with the firearm for your wife. Make sure she knows how to use the gun and what to do if the gun malfunctions.
You mentioned being away at night. Have her shoot the gun at night as well (on a regular basis) to get used to the muzzle flash.
Check your local gun club and see if there are any conceal carry classes that are being taught. Sometimes it's hard teaching a loved one and very easy for someone who doesn't know them.
Is it a revolver or semi auto? If it is a semi auto what condition is it stored in? Does your wife completely understand the "conditions" of the pistol if it is a semi auto? Does she know what "condition" (such as "cocked and lock", mag in well, no round in chamber...) the gun is to be "stored" in at all times?
Revolvers do make things simple for people.
My wife knows that EVERY single handgun in our house is loaded and in condition one (if your going to treat every gun as if it were loaded, it should be loaded).
Honest opinion is that if you want to keep the firearm out of reach of the children, you should lock it up, period. Although I don't have any children of my own, I've been told by friends that they can surprise you on what they can find and where they can find it. Again, if you need to hide it (the gun) from them, they should not have access to it. The ONLY way to ensure that is by using a safe with some sort of combination or "print read" system.
It seems from the events you mentioned that your wife would have plenty of time to access the gun in the event that she would need it.
Spend the extra money and get a good "handgun safe" (per some of the nice ones listed on this thread) and put it by the bed.
You mentioned that your wife can get nervous, make sure she knows where the mossburg (sp? hey, I don't own one /forums/images/graemlins/grin.gif) is. Its alot easier to hit something with a shotgun than a handgun when your nervous.
Heck, thinking about it, you could always mount a streamlight on the AR. I'm sure if anyone saw a woman come out with an AR with a light on them, they would go running.
Since I don't have children to worry about, a weapon is always within reach in the brdroom at night. I've told my wife (and practiced this with her) that if she hears someone in the house at night and I'm not at home, to lock the bedroom door, call 911 and tell them (911 operator) that she shot someone in the house (this will MAKE SURE that she gets a quick response), open the "side door" from the bedroom (opens to a 3rd floor deck, only accesible from the bedroom), let off a round for "effect" outside and then hollar to the intruder that she has a gun and will blow his head off if he comes into the bedroom. She has a "corner" position in the bedroom with a clear view of the bedroom door (other door that leads to the main hallway) so if anyone enters, she has a clean shot with the shotgun.
To some I realize that this may be "overkill", but you need to have a "routine" to practice, an be prepared.
Since you have children, make sure you and your wife "go over" with the children what they should do as well if your wife needs to access the gun. You need to make sure you and your wife know where they (children) are at all times.
Practice does not always make perfect, but it does decrease the odds that you (or your wife) may make a mistake.
By the way, I didn't know that Garrett county had a game warden /forums/images/graemlins/grin.gif
