If you can get a block of peat moss and a bag of untreated (not dyed red or black or "long lasting color" crap) shredded pine bark (should be like sawdust almost) for cheap, I might fold both of those in to loosen up the soil. Of course the peat moss can affect your pH.
And of course if you can run over leaves with a lawnmower and fork those in, that's good stuff too.
