Just go for the old stuff - they love a sing-along and especially the songs that everyone knows.
I look after a small group of elderly folk who fall asleep during the regular music sessions but when we sing the boring old stuff like Michael row the boat ashore or Daisy Daisy, they come alive.
If you're in Geordie land, go for Keel Row and Blaydon Races. Keep your feet still Geordie Hinny is good too!
Robyn