How much time should you bake & then decorate a cake prior to a birthday party.?

I usually bake & decorate my cakes about a day or 2 before any party. But I was wondering if I can do it any sooner? That way it's just done and I'm not having to rush a day or 2 ahead of time. Also how would you store it once completed in the fridge? Or are there any other methods that work better? It is a Chocolate cake with Fudge Icing, it also has Dinosaurs, palm trees and boulders made from Rice crispy treats that are decorated with er cream & wiltons spray food coloring. Any ideas would be greatly appreciated, thank you to all who participate.