Re: Hello and help needed for father....
Much as I dislike friction drives, I tend to agree this is probably your best bet for ease and reliability as well as easy pedaling when not motoring.I have heard nothing but good about DAX and Staton both so you should have a easy choice between them.
LR Jerry has a slick friction shifting setup...he might be willing to help steer you towards the good stuff.
Avoid the bumblebee bolt on. Lots of complaints here about it being poorly made.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.