Sixty years is a long time to know someone, you really bonded together with interests other than a common religion, after your wife it would appear he is possibly the most significant person in your life, and he will have the utmost respect for you.
There's much to be said for rekindling the bonds of friendship, there's very little, if any, downside from your perspective and rather than be sad you have left "the truth" he may have a secret admiration for you being your own man, whereas despite his intellect (and his doubts) he's suspended his critical thinking abilities, and he knows it!
I'd go for the interview.
Snapdragon