J.T.
I would not use anything with dairy in it, to begin with, but I really think they will be okay.
Cold baked goods are nasty (my personal opinion- as is cold pasta). I would not put them on ice (or ice packs) in a cooler. I would frost them when I got there as people wanted them.
Make a cupcake bar! Frosting, sprinkles, candies, cookie crumbs, etc, and let everyone decorate their own cupcake.