Hi Exo,
Welcome to RetouchPRO! Sounds like you've got quite a project ahead of you.
David gave you some excellent advice. One thing that I'll add is that if you are planning on enlarging any of your photos, I wouldn't go past 2x in size. In my experience, there just isn't enough information in the print that the scanner can pick up past 2x in size. (Put another way, if you are shooting for a 300dpi final print size, you can scan at 600dpi to allow you to adjust the size to 2x.)
A GREAT site for scanning tips is
www.scantips.com. I just looked and there is even a section on restoring genealogical photos there now. Wayne has an extensive explanation on pixel dimension & dpi that may help you. If you are very new to scanning, you might want to purchase his book.
Always scan photos in color. Like David said, even B&W or sepia prints most often have different information in each of the channels which you will find helpful when you start to restore the photos.
Storing to floppy may be a problem if you're hoping to print larger photos (i.e. 8x10). A floppy can only hold 1.44MB and the only way you can get down to that size is JPEG. Unfortunately, you may lose some quality that you're not happy about in the compression process. Whatever you do, be sure to save the final version as a TIFF (or BMP) so that you have a version which hasn't been compromised by the JPEG compression. I think you'll find very quickly that a CD burner is essential for storing photos off of your hard disk. I can't imagine life without one. You may be able to get by with a ZIP disk for taking photos to a lab for printing, but for long term storage, it's hard to beat the price per megabyte that you get with CD storage. (Of course, I've now got my sights set on a DVD burner b/c the storage size is so large, but need to wait for the price to come down a bit.)
Standard sizes of photos seems to differ slightly between metric and non-metric countries. So, for example, a 4x6" print in the US equates to a 10x15cm print. Other "standard" print sizes are 4x5", 5x7", 8x10", 11x14", 16x20" & 20x30". You may also find some labs print 8x12", 16x24" or 24x30". Some of the desktop Epson printers print up to 13x19". The wide-format printers can print up to 44" (with just about any length.)
I recommend that you talk to the lab you want to use and find out what they offer in terms of sizes - and what they require for file formats (TIF, JPG, etc. and what resolution) to print.
Hope this helps,
Jeanie