We put up white fence around our back yard -- now areas that used to be dark are a lot brighter. Also, my neighbor's house is a light tan color and the garden located on the north side of my house is brighter when the sun is shining directly on THEIR house.
You may not want to paint the house or the garage, but maybe you can just hang a white material -- maybe something like the floating row cover -- on the walls. Just another one of my crazy ideas.
... OR you can get even crazier and hang mirrors.
Don't forget lettuce. You can also grow Blackberries, Blueberries, and Wild Strawberries (Fragaria virginiana) -- not sure about cultivated strawberries. Maybe Cucumbers.