Maybe leave out anything that refers to dying. I was once singing for a group of terminal patients in a hospice ward, and blithely waded into Sloop John B... only to hit upon the "I want to go home" line...!

What about the Beatles' Ob-La-Di? I always liked it because it's so joyful and fun. Also maybe Da Doo Ron Ron? Both these songs are lighthearted, with easy-to-follow choruses.

Another time, as part of a choir, I did an informal Christmas concert in a a nursing home. Afterwords I heard one of the other singers say to a resident, "Did you enjoy it?" (Something I would not have asked.) The old lady replied, "No, I didn't. The music was nice but it made me too sad." So be careful what material you choose. Of course Christmas is loaded with family associations and memories, so perhaps any holiday songs would have depressed her. But it's something to bear in mind, so perhaps stay away from death & dying. Those folks aren't going anywhere -