With scanned pictures, the bigger the better. Have them scanned on the highest resolution possible. I used to do weddings, and I would always have to scan the pictures myself. I’d scan them on a high resolution (usually to jpeg format) and then import them into FCP. From there, you can resize them easily. If they are too big, size can be decreased without the picture going to crap. If they are too small and you enlarge them, they start looking crappy.
The other good thing about having them large is that you can add a little bit of motion to them so it isn’t so boring. But the absolute minimum resolution you are going to want is 720*480
NeutaMac