Jerry-

Certainly with a chorus, a refrain, or both!

And probably it is better to choose a shanty/chanty/chantey which you expect most people to be familar with, unless you're particularly good at commanding attention make some effort to teach a novel chorus.

There will be opportunities throughout the weekend to sing the quiet or longer ballads to smaller groups of people but the large late night events are shanty shouts. And seldom is anyone "invited" or "encouraged" to lead a song. You have to sieze your moment and then nail your song.

Cheerily,
Charley Noble