So sorry for your friends loss.
I vote for using 5" squares for a disappearing nine patch. Maybe use 1 1/2" strips to window pane it. Missouri Star Quilt Company has a nice tutorial on the Window Pane D9P. When I was a kid we always used the good pieces of worn clothing to make quilts. It wasn't until after I retired and started taking quilt classes that I bought new fabric. We took old sheets and cut up into squares to use for the foundation than took bits and pieces of clothing fabric. Made several really scrappy quilts.
How about just framed nine patches? That way the pieces would be big enough to recognize?
A nice touch would be an embroidered label. Do you have an embroidery machine? If not, maybe someone you know or maybe ask at your local quilt store.