As a Wisconsonite who was raised as a Lutheran, my first thought was also lutefisk. But I imagine you'd like these party guests to continue speaking to you after the event. :p
So, yes, lefse would be a good choice. They're not particularly difficult to make, but they are a bit time consuming. You have cook and mash the potatoes for the dough, then you have to roll each one out very thin. And, traditionally, they're fairly large, so you need a big pan. But I suppose there's no reason you couldn't make them smaller.