Q. Dear Donia,
A. Dear Daniel,
I am glad to hear you are storing your collection is acid-free, lignin-free boxes and sleeves.
Beyond that, you want to store the materials somewhere with a stable temperature and relative humidity so no basements or attics. A bedroom closet is a good place if you have the room. For those materials you want to frame, if you are framing the original, be sure to use museum-quality mat board for matting and mounting and UV blocking glass or Plexiglas to reduce damage from light (but it won't completely prevent the damage). If you plan to use a print from one of your scans, you can use less expensive matting and glazing materials.
As to scanning, as long as you scan at the best resolution you can and save the image in a non-proprietary lossless format like .tiff and, most importantly, only scan the image once, you will not cause any long-term damage. In fact, you could prevent damage by being able to display and handle prints rather than handling the fragile originals. And, it is a great way to share your family story with everyone.
This is the approach I have taken with my own family collection.
Best of luck!