What a loving undertaking.
I have done quite a few signature quilts. I gather the signatures before making the blocks so the quilt won't be harmed by careless signees. On the first one I found some people just plain 'ol didn't 'get it' and signed into the seam allowances of the fabric provided. So I put on my thinking cap and decided what to do. The people now signed only the signature fabric that I had prepared, precut, and put inside of a manilla file folder that was the same size with a window cut out for where to sign. I also had a line on the inside of the folder so their signatures might be centered if that is what they wanted.
You could always have the finished quilt posted somewhere online for those who want to see the finished quilt.