To come at this from a different direction for a moment, Ellen Langer might suggest that the best apps for the elderly may be non-apps, or simulations of old tech:
I have observed that professional computer scientists, who have been using computers since the 1980s, are incredibly productive using a software stack that has not changed essentially for decades: Unix, the shell, emacs/vim. Even python, one of today's darlings, is almost a quarter-century old.
George R.R. Martin wrote, and still writes, Game of Thrones on an MS DOS box running Wordstar.
So, combine Moore's law with Clarke's law, and what do you get?
Ontology recapitulates phylogeny; technology recapitulates skeuomorpology.
So, instead of giving him an Android tablet, with a new interface to learn, why not retrofit a "family" channel into his existing TV?