Dear B Keller,

I am very sorry to hear of your father's passing.  It may be best not to get
caught up in quoting Twain himself.  Your father was every bit the human
being as Twain was.  Pointing out how your father liked Twain & what they
shared in common (morals, humor, anything) would certainly stand grand
testimony to both men.

My heart goes out to you and your family.  I think it likely that what is
important is already known to you in your heart, and just telling the story
of your father's admiration for Mark Twain would easily accomplish the
fitting tribute you want to make.

With Best Wishes,