Now this is my home territory - though from a British perspective. Given that, and the fact that the audience would probably want something bright and breezy, I'm going to suggest a song by the immortal Percy French. (Purists can leave at this point...)

It's probably not well known across the pond, but "Are Ye Right There Michael, Are Ye Right" (as it's usually known) is a grand old comic song based on the writer's experience of a narrow-gauge line in Ireland that is (sadly) no longer with us...

It has a good rumbustious (loud!) chorus that is easy to pick up, and the song lyrics lend themselves to characterisation and a comic approach.

Though whether you can find a copy of the song and learn it (though you may already know about it) in good time for the big day is anybody's business....

Good luck, anyway!

Train Guard