It's rather surprising, but I can't think of any well-known Irish songs with a chorus that the general public can join.

Wild rover is too slow and sad, even if it does have a chorus. And it's bad karma for a wedding.

Are your listeners going to be Irish or Polish? Here are a few songs that are apt to be known by both groups.

Oh Susannah
Edelweiss
Happy Wanderer
Loch Lomond