I believe I share your feelings about making contributions 
to the maintenance of Marion's Farm. (Like everything else in life)
this is an interesting situation potentially edifying and productive.
I have no affirmative advice, but I would seriously consider making
Micha a co-beneficiary, if not indeed the sole beneficiary of regular
contributions to their farm. I never made inquiries, and in her letters 
Marion made only perfunctory references to Micha; but I remember vividly 
a conversation from which I inferred that it was she who divorced him, 
and referring to the tragedy of Micha's life with his second wife she said: 
Poor Micha he deserved better.

I suspect that Micha and Barbara are lonely, and are in desperate need
of someone (like yourself) who will mean to them - and do for them -
what you meant to - and did for Marion. Their need for family is analogous 
to Marion's. When next you have time, I would like to talk with you about 
the potential dimensions of the relationship of our family to theirs.