New Coop - Surface/Chicken Question

I'm brand new to this, although I've been researching for almost a year. Going to get a coop with attached run and two or three chickens. My chicken lady says three are better. I'm thinking of a Favorole, Turken and a Silkie. The run finally comes in two days and I have to put it together. It's 6.5' long by 3.5' high by 2.5' wide. I have an old raised vegetable bed that I no longer use because it's in mostly shade from the redwood trees above which would be the perfect size for this coop. Right now there's dirt covered with moss in the bed and I'm wondering whether to put the coop right on this or get different media to put on top before placing the coop? I read about bark being a good media - but I've got those redwood trees with all their dried "droppings". Would redwood be a good surface to put my coop on? (The coop itself has a raised coop area - of course the run sits on top of the surface). And do you think those three chicken breeds are a good choice? They would be coming as pullets. I'm in a residential area with a medium sized yard (for california!) just about 3000 square feet. Thanks for any help!!!