Hold hard. Three things need to be cleared up.

Are you the only act?
Are you working solo, or is the audience supposed to sing along?
Will the audience be listening to you, or is this a pub deal?

I ask the last question because recently I went to the Celtic center to hear a band. When we got there, it was just a drinking fest. Instead of people sitting in chairs, listening, people were around banquet tables, and the bar was doing a booming business. People were drinking and yacking, kids were running around screaming, and the band could hardly be heard. As far as I could tell, nobody was paying attention to them at all. We left.

If the set-up is like that, just do the chestnuts. (The advice I gave upthread is for a more polite setting.)

I don't know where you live, Matt, but from my experience, if you want Americans to sing along, lower the pitch.