For what its worth, I had the same project.
1) Buy a good quality photo scanner. I personally like the Epsons. The V600 is nice. Realized each whole increase in print size will require a further 300 dpi. I typically scan at 1200 dpi. Unfortunately, higher resolution means longer processing time.
2) Have a computer with a fast processor. As discussed, resolution slows processing at the scanner. It also increases file size. Fast processor will be needed.
3) Scan in a lossless format. Don't scan jpeg. Scan TIFF.
4) Adopt a naming convention which makes it easier to locate originals. XYZGroup-001,tif, XYZGroup-002.tiff etc.
5) Get an external hard drive (or two). Scan to one. Duplicate to the other. Nothing worse that loss of that data (and time). Make more backups and distribute to alternative locations (office, family, etc.). In case of destruction of one location (fire), you have offsite backups.
6) Continue the real time recollections with your grandfather. If vision is decent, then use a laptop or TV to display the photo (which will also display the file name) and use a video recorder aimed at the monitor (or TV for output) with a digital audio backup (iphone is one option, I prefer the digital recorders). Walk through the photos as scanned with the standard questions. Allow time for random reminiscences.
7) Put original images in acid free envelopes. I prefer the ones from Archival Methods. The photographs and negatives degrade. Acid free sleeves ****** the problem.
8) Build a database of the images. I like Filemaker Pro. It allows you to build a drag and drop database. It also allows you to drop thumbnail images (jpegs) into the file (I use IrfanView to batch jpeg images in a folder and drag and drop). Its easy to build the index, identify who/what/when/where is in an image, then drop and thumbnail. It makes it soooo much easier to later find that one photo you are looking for - so-and-so was in a photo in Italy - when you can run the search then scroll through the records to find that one photograph.
