If you want the audience to sing with you, there is one song that everyone sings, the young, the old and the in-between. It is "Somewhere, Over The Rainbow". I can't explain the hypnotic affect of this song but I have sung it in school assemblies, at birthday parties, at weddings, at senior facilities, at folk clubs and in concert and, I swear, as soon as I start the audience joins in as if it was some kind of anthem. I guess that everyone knows it from the movie and singing it makes one fell young and hopeful.
The chords are interesting but easy.
Let's hear it for Toto.