Excellent idea, Frank. There are many historical events that we commemorate, but not necessarily celebrate, because they were events that shaped us as a nation. Certainly, June 6 is commemorated as the date we invaded Festung Europa at Normandy -- nobody in their right mind "celebrates" that awful date of carnage, but we commemorate it because what our heroic troops did that day changed the world.
I can't imagine that Congress will let the sesquicentennial of the Civil War pass uncommemorated. Even the vocal minority can't shout that loud.