Thinking about it more Rob, with that many to do, I'd set up a router sled. Just stick them to a flat surface with some carpet tape and rig up something like this. Flatten one side, flip them over and finish to thickness then sand the tool marks out. That way you get uniform thicknesses and perfect flatness. If it was just one or two, I'd use a belt sander but for that many, this will be faster and give more consistent results.
