Just an idea here. You might want to contact the director of activities ahead of time (maybe a few weeks before the show) and have the director ask or nurses aids ask the patients three songs they remember as some of their favorites from the past. If patients can write it themselves on the paper that would be fine too. If not, the nurses aid or director can write it down.
Then you can go there to collect the papers with the songs written down and get an idea ahead of time as to the songs they would like to hear.
I know one favorite song of some older folks in the homes is, "When Irish Eyes Are Smiling" and some Bing Crosby songs too.