I think your best bet would be a copy stand/overhead scanning setup. This type of scanner is more expensive, but you do not have to turn anything upside down. Some libraries have them to scan books quickly and can do so two pages at a time. However, they might not be intended for photographs, in which case I would look into seeing if there are any companies nearby you that specialize in graphic arts scanning. They may have a copy stand intended for fragile works.
The other option is to take photos of the photos, assuming you have the right lighting and a very good camera.