First off, do NOT sharpen anything with the scanner software. That will accentuate the grain.
As far as reducing the grain, I've had good luck with
Neat Image. It takes a little experimenting before you learn not to overdo it, but it has really helped some of the old photos I've been working on lately. I've attached a before/after example of one that I've been working on this morning so you can see what it is able to do. I didn't want to completely remove the grain in this photo because it would have removed some of the fine detail as well. But, I think it helped immensely. (Please realize that this is just a before/after of Neat Image - not a finished version of the photo just yet.)
Jeanie