Curly,
When my granfather was in his 90s, he was deaf as s doorknob (almost); you had to yell in his ear to be heard. Blood clots had settled in his thighs, making his leg muscles unusable. And if he saw at all, he didn't let on ...
But the mind was still there ... and if anyone needed a problem solved, he went to Grandpa ... I can still see them standing in line on a Sunday to take turns yelling into his 'good' ear.
But they always walked away with an answer to a crippling problem, usually shaking their heads as if to say, 'Now, why didn't I think o that?'
Moral of the story is: don't let your dad sell himself short ... he still has 50+ years more experience than almost anyone in your family ...
Best wishes for a New Year ... and your dad will indeed be in my prayers!