I have made a 9X13 marble cake for my Grandson's birthday tomorrow. I have to travel 3 hours to get to his house. The question is:: Will milk chocolate make the trip if I decorate it tonight or should I wait until I get there tomorrow?? It is supposed to be around 50 degrees in the morning with about 49% humidity. The icing recipe that I have used is the Chocolate Buttercream Dream on this site. Thanks for any advice you have. I am desperate.