When you are able to hear, see properly, walk straight without the help of a stick, and you are able to co-ordinate yourself without help, then you are in a good position to learn how to drive. Not forgetting the zeal to learn, you can do anything. At this age you cannot force someone to do something, but if the person has asked and is willing to put in the effort, why not! Am sure they will be able to learn faster than you think. It will take a lot of patience though before they get the hang of it. They are at the stage of life where everything is slow motion, there is really no hurry for anything. If you know you will be impatient do not start with them get someone who will walk with them to end, and someone who understands them. I have seen quite a number of oldies who are still driving in their old age, so it's no big deal. Things have been made easier nowadays with the automatic cars, they don't need to keep changing gears that will make things hard for them.