I'm sorry for what you've had to face.
My family recently had to deal with a similar situation.
My grandfather (alone - and not necessarily stable to begin with), reached the point that the family got together and made the determination that ALL firearms should be removed from the house.
After some discussions with my grandfather, and convincing him that he really no longer understood or had any real grasp of the world around him....
About a month ago, all 'heirs' gathered to receive their allotted firearms, and the few that are inclined to such activities took applicable reloading tools and supplies as well. The designated 'heirs' not privy to said meeting (myself only, as far as I know) received their inheritable firearms after the fact.
(I was the ONLY grandchild to receive one of the firearms, and it was one of the most sought-after pieces - being
believed to be highly valuable by my grandfather's children, but not
actually valuable in reality.
My Grandfather left it to me because I
knew what it was and treasured it for family history, rather than being someone that
thought they knew what it was, treasuring it for perceived value. He knew that I understood the true [lack of] value of the firearm, and wanted to ensure that family history came before a pawn shop. And, for that, I am truly grateful.)
It's not fun.
It's not pretty.
But, unfortunately, it's an unavoidable eventuality.
In my family's case, some incredible 'blowback' occurred after the fact, that resulted in ridiculous family drama that has not yet been resolved (and probably never will be). But, my grandfather, when cognizant enough to understand where his precious firearms are going or have gone, continues to support the decisions made. All else going bat-crap-crazy, he has affirmed multiple times that the current possessors of his firearms are exactly who he wants them to be with.
He may not know how to wash his hands or get a drink of water any more; but he always seems to understand where his firearms have gone - and he approves of the decisions made.