This is a really tough issue with some "spouses."
It seems to all depend on how the other person was raised.
You can go with the status quo route, or the subtle manipulation route, or the lay down the law route, or just do your own thing and ignor the results.
If it were me, in your shoes, I would first buy an nice gunsafe. Then put your valuables and important papers in it, birth certificates, deeds, legal documents, in a fireproof box at the bottom of the safe. Jewelry, cash, cameras, laptops, somewhere in the shelves. Then I would just find and shoot and buy (in that order) your ideal handgun (pistol or revolver) and ammo. Keep that at the top of the gunsafe on the top shelf, so the kiddie cannot reach it at any time.
Then decide on your level of security. Under low security, the gun is unloaded and the gunsafe is always locked. Your wife *should* have no problem with this. This is similar to stand-down conditions in any military armory.
Under high security, the gun is loaded and chambered and on the top shelf of the gunsafe, and the gunsafe is open. This might perturb your wife however. With kids in the house, this is not always a very good idea, sometimes even a bad idea.
Either way, an unloaded gun locked in a gunsafe with ammo on a different shelf, is better than nothing. It takes a few moments to get ready for defense, but it is better than nothing. You need to unlock the safe and load the weapon. That all takes time.
A loaded gun on the top shelf of your gunsafe which inside a holster goes under your pillow before you go to bed is the highest state of readiness and requires only a few seconds to withdraw and shoot.
Don't give your wife or kid(s) the combination to the gunsafe. If she needs something out of the safe then get it for her, jewelry, cash, etc. Only give your estate lawyer the combination, so he/she can get into it if you die in a car accident etc.
Then just go with the flow. After 20 years of marriage, I am sure things will work out ok after awhile.
It is your responsibility to protect your family. You cannot outsource this to 911.
You also need to protect yourself at all times, and not sacrifice yourself to the pacifistic defeatist whims of your wife.
It's all good, some of it is better than others, but it is not worth dying for no matter what.