how to scan old photos with minimum degradation

I have a bunch of typical sepia color fading old family photos. I am going to scan then with Epson software at 600 DPI, 24bit colour, Tiff format, unmasking on, original target size, autoexposure off. I want to copy so it is as close to original as possible. If I decide to make changes to the scanned photo later, can I then add unmasking, and other colour histogram changes or is it best to do so at the time of scanning? I want to minimise degradation of the image.