I love your sun/moon design & I'm going to take time to draw it out because I have this space panel fabric as well! An idea just came to me to enlarge your sun/moon and put it on the backing. I puchased glow-in-the-dark thread to go with it.
Your story is the heart of a grandma. You made a great quilt and I think you should tuck it along with this thread to give to your DGS and his mother when he is a bit older. We understand the time, frustration and love that went into this quilt. Thanks for sharing.