I would suggest that he become a business advisor to small companies. His expertise is invaluable and he could be useful immediately.
Possibly, if his father applied himself, he could find himself a niche in which he would be adequately competent within 2 years. To include being a freelancer or independent developer.
As you alluded to, because of his father's business background, he might do really well in sales for a software related company or starting his own business.
> Being a CEO, CCO, etc... We can assume his father is an intelligent and successful person.
Being unable to continue working as a CEO/CCO suggests he's not currently very successful, and to put it lightly, CEO "intelligence" (whatever that means) doesn't necessarily translate to the kind of intelligence necessary for software engineering
I had a friend ask me same thing as OP. He was 50, out of work at the time (had been in a trade before) and wondered if he could get into programming. I don't want to discourage anyone from learning to program because you can do a lot of cool stuff, but to be seriously industry useful isn't a matter of months and a few online classes but rather some dedicated years.
And (this might be an unpopular opinion) it's much harder if you don't natively think a certain way. Some otherwise smart people find programming pure torture and the chance of them going through the years needed is pretty low.