Not recently, but I spent quite a few summers as a child on Flathead Lake. I don't recall much about the food, except that they used to grow the most amazing cherries there. The flavor is easily the most powerful memory of my childhood.
As for things to do, drive the Going to the Sun road.
[T]he only American roadway designated both as a National Historic Landmark and a National Civil Engineering Landmark.
ETA: I'm not sure how far you're looking to stray, but twice when we've been out to visit Yellowstone we've stayed at a fantastic place just outside of Bozeman (5 hour drive from Bigfork) called
Howler's Inn. It's a B&B attached to a wolf sanctuary.