To expand on another
Scanning. Tedious but you can see real progress.
Sorting metadata (times, dates, people involved, locations...). Tedium like you would not believe.
That said I would be careful of information overload, or the photo equivalent of pirate syndrome. Though photos were still variously special things until around the time we all got digital cameras there will almost certainly be junk within it.
If you can arrange something like each person, key times in their lives, notable events and such like rather than 10 angles of the same wedding and a picture of a cat nobody alive will remember seeing then that can make life easier. Now you do have the different strokes for different folks thing (if there is a photo of said cat it might have been important to them and "so and so always talked about it, was nice to see it" can happen) but most can at least appreciate a high days and holidays approach.