Unfreezing frozen cakes?

I have to make a 3 tier b-day cake, I have them in the freezer now and I need them for sat. I'm going to ice them on friday before the party, I have to drive 4 hours to NJ from CT, should I leave them frozen for the trip or should I defrost them before hand? And how do I defrost them? Leave them in the fridge or out on the counter, in the plastic wrap and foil?