Minky is nice, but it is $13 a yard and more everywhere I've seen it.
These are grown men and women the quilts are going to for QOV. They really might prefer a backing made to represent their branch of the military. There are lots of nice Marine Corps, Army, Navy and Air Force prints out there right now. Some are old fashioned looking with uniforms and aircraft from the 40s. Some are just the logo.
I know this is what the military people in my life would be proud to have as the backing. They are each proud of their branch of service!