Susan, if by elderly you mean folks in their sixties, remember that they’re the first rock generation. Instead of something soothing and bland, they might like “Long Tall Sally” or “Roll Over, Beethoven.”
How about “As Time Goes By”? Because of its association with CASABLANCA, many generations love it. “Blueberry Hill” is associated for my generation with Fats Domino; but it’s actually older than that.
Ray Pool American Classics. Some of the songs in this book, volume 1, are not hard. I get a lot of compliments from older people when I play these and first got the book because one of the songs was the anniversary song for a couple having a 50th wedding anniversary party.