Now that you have the lens, I would do a test to find the sweet spot in terms of aperture. Probably in the 5.6 to 11 range, but that will depend on the lens and the distance from the subject. The 100 2.8 is a very sharp lens, even wide open, but it's good to know. You might also want to try processing in C1. In every comparison I've made, C1 had lower noise and slightly finer resolved detail, when compared to even the latest version of ACR. The choice, however, is yours to make. Shooting old photos, you may or may not want to retain any age coloring they have, but you certainly won't need any plugins for making them neutral black and white. Good luck, this sounds like a tedious project.