I've been playing retirement homes for about five years and the one thing I've learned is to keep the majority of the music up-beat and happy. They love music with a good solid beat that they can tap their toes to. You can vary the program with a slower number now and then, of course. But I would definitely bias your program in the direction of lively. And of course using tunes that are familiar to them (of their era) is good as well. You'll likely see some of them mouthing the words to the songs they recognize.

I typically may use some Dixieland, swing, Latin, a polka now and then, maybe an upbeat country tune, a boogie, etc. and then intersperse the occasional waltz and ballad. It seems to work OK.
Paul C.