I would really suggest you freeze the cake. Each tier in its own box, double wrapped in plastic. Transport in an ice chest ON TOP of dry ice. Set it out - still wrapped - and let it thaw. That way any condensation will be on the wrapping and not on the cake. We took one buttercream and one fondant cake on a 23 hour ride from Texas to California. One was my son's wedding cake. They both made the trip fine and were just as fresh as if I had just made them.
7/11/14 at 4:26pm