Not to grouse or anything at somebody who is approaching 100, but Moonlight Sonata should be left alone, if possible. It is like putting maple syrup on an already iced cake (I know, some people probably like it that way). There are other beautiful Beethoven songs that your friend might like, which have a Beethoven-like feel to them. "An Die Ferne Geliebte" is one of the most beautiful song cycles (and the inspiration for Schubert, Schumann, Chopin, Brahms, etc., etc.), and there are individual songs, like "Adelaida" which are heavenly.
yours, Peter T.
P.S. The Lucy-Schroeder song from "You're a Good Man, Charlie Brown" is fun, just to show that I am not a prude about this. Not as good as "A Book Report on Peter Rabbit" or "Suppertime", but O.K.