Well, just taking the keys away doesn't always work. A senior I knew happened to have another set the family did not know about, did drive, did forget where she was going halfway through the trip, and create a big stir. Another senior who shouldn't have been driving had NOT given his child POA or any control of his affairs. When he was told not to drive and refused, his children took his car away, and he promtly called his attorney and changed his will, disinheriting both of them in favor of a charity. In another case, mom was just getting really old, had a number of children, most of whom agreed she should not be driving. The one who didn't agree bought her a new car when the old one was taken away, and yes, within a few weeks, she had a serious wreck which precipitated her death. Talk about a nasty family feud.
With or without Alzheimer's, folks, no amount of expired license is going to make it impossible for a person to drive, I've known lots of people who drove for years without licenses, but nobody drives without keys, unless someone gives them another car to drive, and I have known seniors who have actually swiped other people's cars when they weren't paying close attention, offered teen aged grandchildren money to borrow their vehicle, etc. !
I suggest a bit of helpful misrepresentation in the neighborhood of, 'Mom your doctor has told the GOVERNMENT and they have said you can't drive anymore, and if you did, they'd probably fine you and me a big bunch of money!" And then you take the means to drive away, keep blaming "the authorities." Better they rail at the authorities than at you personally.