Have to agree with many here, don't keep your gun in a crawlspace whatever you choose.
My bro is a cop, he selected a .38 Taurus revolver for me. For someone who is not a lot used to guns (I am pretty well but not sure how I'd react in a bad situation), Semi auto's tend to jam and you have to be well acquainted to be able to unjamb quickly it in a bad situation. Not a good choice.
Shotguns I guess are good but are more expensive and if you go on a trip or have to bug out, they're considerably larger and more difficult to take with you.
I gotta go with what I have, the .38 revolver, in a nightstand by your bed. And then train, train, train. You can also train with a revolver at a range whereas you may not be able to with a shotgun.
If you have kids, it does lock but fishing for the key in a tight situation is time lost and perhaps you or family dead. Best to train them to shoot and how dangerous guns are. If they shoot a .38 a couple times, I think they will be scared off of wanting to use it. It's not got a horrible kickback but is certainly powerful.
PS. You're gonna have a ton of responses. .38 Taurus revolver, small enough to carry, powerful enough to hurt and won't jamb like a semi-auto. Remember, train, train, train otherwise you are a detriment to yourself and family because you would be uneducated and too scared to be confident of what is going to happen.
Your bro is wise, Taurus is a good reliable gun at a reasonable price.
Semi-autos are not really all that jam-prone, if they are fed, maintained and used properly, but revolvers are simple and in a high stress environment, simple is good.
My Rem 870 disassembles into pieces that fit nicely into a suitcase or gym bag