My condolences on your loss - it's never easy, but you have come up with a project that will keep you busy - isn't quilting a blessing? I suggest you use Pigma pens. I see the use of sharpies above, but am unfamiliar with those in the wash, and would worry about them running. The border on the block must be clear to those who sign so that they won't write in the seam allowances. Best of luck.