I agree with the many who have chimed in, and applaud your daughter that she said to leave it to. But then, I know you are wanting this to be an extra special quilt, and don't want to feel discouraged in the final product, so I have 2 suggestions.
1- If the square in question, truly is in the center - what if you print a poem or pic to coordinate, then appllique it over that block?
2- Do an applique similar to these animals over your block:
http://www.ohfransson.com/photos/quilt_gallery/
No matter what you decide, it will be a family heirloom. And knowing your health history, it will probably become one of the most cherished part of the quilt as your daughter and grandchild look at it. "Mom could barely see, she felt really crummy alot, but look at the time and the workmanship she put into this most beautiful quilt. We know how much she loved us, and this quilt shows that love".
Good luck, let us know what you end up doing.