Definitely get her too!
My biggest hint was that I made the cakes about a week in advance and put them in freezer bags and popped them in the freezer. I then made a batch of just plain chocolate icing a few days before the party and 'dirty iced' the cakes whilst still frozen. It's a layer of icing to go under the top layer, it smooths the cake and stops your top layer of icing from being all crummy.
Once it's dried, back into the freezer. The actual decorating of our cake was done on the morning of the party, but the day before would be perfectly fine
(It also helps that DP is detail oriented when it comes to stuff like that- notice it's *him* icing the cakes and not me? He elbowed me out of the way and took over, because according to him, I was doing it completely wrong!)