Somehow my daughter will be 19 years old later this month.  I have no clue how that happened so fast, but here we are.  Fortunately, I have a work trip that takes me right through her college town on her birthday, so I'm taking her to lunch on my way to my conference.  I'd like to take a cake for her to enjoy with her friends that evening.  I thought I'd bake it, decorate it, and freeze it in a wrapped box.  Should I transport it in a cooler to slow down the thawing? Or would it be better to transport it without insulation?  I'll leave home early in the morning to drive the six hours to meet her for lunch, and then she'll probably wait until after dinner to eat it.  I'm not planning anything elaborate.  It will probably be an 8" round with watercolor buttercream and some buttercream flowers on top. 

You could freeze the cake, already in a box, wrapped well.  It would probably still be cool when you arrived, but not frozen.  If you prefer not to freeze the cake, you can just have it well chilled from the refrigerator and create a portable cooler for transporting.  The ice will keep it cold for several hours.  Unless you are using ingredients that require refrigeration, I think you will be fine, even with the cake thawed.

Your plan is right on:)     I would use a cooler to transport as you said  fz 1st well wrapped