I second the advice given by Greg Davis. Since these materials have survived up to 100 years already and cannot be replaced, copy them and correct the copies. Store the originals in acid free storage containers and possibly with some desiccant material (not in contact with the photos). We came across a 100 year old print of my mother's family including her grand father. I photographed it with 4x5 film and printed on warm tone matte paper achieving a very close likeness of the original. I also scanned the new negative to make some repair corrections and to make some digital copies on heavy weight cotton fiber paper for the family. It was not difficult to produce what appeared to be an original old photograph.