Friday will be fine, I would bake the cakes, and when cool, fill, stack and crumb coat. That will keep the cake moist.
Also it allows time for the cake to settle, and then I would decorate the cake on Saturday. Alot less stress when you can do it this way.
I made myself a birthday cake, epicurious double chocolate cake with SMBC filling/frosting and MFF on 1-26-10. My mom still had the leftover hunk in the fridge when I stopped by last Tuesday and had a piece straight from the fridge. So moist and dense. Yummers.
I did a little experiment this week. I baked a cake and fully iced it in buttercream on Monday afternoon. I've been eating it all week to see a texture and moistness change. It is still as moist as Monday! I left the cake out of the fridge all week. I'd say a good 3 days would work.
Everything I see in the world, I think of what cake pan it's shaped like!