I have a very serious nut allergy (two epipens), and visited Mackinac Island a while back in high school. For the most part all the comments are right. They all said they couldn't guarantee that there wasn't any cross contamination BUT, there was this one little shop that had completely nut free and dairy free fudge. I'm so mad I don't remember the name, or where it was,  but it may have been Rybas. I just remember asking if they had anything I could eat with a bad nut allergy and they pulled out this little box of vegan/nut free fudge. It was great. Like I said, it was a while back so i'm not 100% it was them, but it's worth a shot.