Awww, so sad. I'm sorry for the family. You got a lot of good answers. I'm sharing something I did here:
When I made my parents an album quilt I had all four of us sign it and add sentiments, along with their 9 grandchildren.
My parents lost their last child, my little brother at birth.
I had to find a place for him. So I put an angel applique with his name and date on it. They loved it :)
You'll figure something out.