My father the teenager and grandkids he ought to meet

Brayden

Kyle

My elderly dad is proving to be a difficult parent.
He's evasive.
He doesn't do what he's told.
He's defiant and you never know for sure what's he's going to do next.
My brother and I feel like we've suddenly inherited an 87-year-old teenager.
Because the two of us live the nearest to him, it falls to us to help him now that he is no longer able to take care of himself. We need to get him to the doctor, the bank, the post office and the grocery store. There's also the barber shop, the library, the VA hospital and the church.
He can't drive himself although he's pretty sure he's still sufficiently able.
For years, he's been a pretty self-sufficient albeit disinterested father.

Conner

He came and went pretty much on a whim, only stopping by occasionally and briefly. He was not really into hanging around the grandchildren.
However, he was always quick to point out that a man's value can be measured by his grandchildren. (Apparently one has to skip the children. We're just so much chopped liver. Actually, that's come out more cynical than I intend. I know he means well when he says things like that.)
He's been a spendthrift and not too careful with his resources.
At one point, he bragged about running up credit card bills that he would never have to pay because he'd die and it'd be impossible to collect from him.
It's been somewhat worrisome but he was living his life and we were pretty much left to live ours.
Now that he's of an age and health that we're having to help him get anywhere he wants to go, things are different.
The doctors have told him not to drive. The Veteran's Administration has told him not to drive. Those who've ridden with him anywhere tell him not to drive.
But he's convinced that because the expiration date on his license says it's valid until 2012, he can drive despite the advice of experts. He's sure the VA examiner had it in for him (I was there when the poor guy had to tell him he missed pedestrians and road signs and backed up traffic behind him for blocks. His reaction time was 8 times slower than it should've been.)
So despite our best efforts as a family, we can't keep him from stealing the car and driving away.
My brother bought one car but there's another in the garage and when cabin fever gets too great, he and his wife slip out to nearby restaurants across busy roads and into heavy traffic.
What is a family to do?
You can ground a teenager, put a child in time out.
What do you do with a full-grown parent?
And what happens when I'm one of those?