I agree with all that Tony said. I've done the 'Scanning the parent's photos' project and believe me...

1) Ok, it seems like a great idea just now BUT; the novelty wears off after a couple of hours/minutes/seconds. And once you've told Grandma you'll do it, you need to finish the job!

2) All your hard work probably won't be appreciated in the slightest. They'll still look at, and use the album and ignore the scans!

3) You need to scan them one at a time for the reasons Tony mentioned.

So unless theres a real need to do all these scans, I'd be inclined not to do it yourself - pay a younger nephew or something to do the boring repetitive task for you!