I know what the "experts" say, but I guarantee that someone along the way will toss old quilts in bad condition, I have seen it time and again, so.....I vote to fix them.
Make tracing paper templates of the pieces that are needed and find fabrics that are similar in feel and tone to the damaged ones. Applique these over the damaged ones. If whole blocks are shot, make a new one and applique it over top of the old one and hand quilt it if needed. THEN make a label that states that the original maker was ______and that the restoration work was by granddaughter_________. This makes them double valuable to family members, and if somebody 100 years from now wants to put it in their museum, they have the information, and can unsew your work if they desire.