You may want to look into outsourcing your work to a company that specializes in photo scanning.
MacWorld had an article in October 2009 reviewing 3 online scanning services:
I placed orders with these three
scanning companies: ScanDigital.com,
DigMyPics.com, and ScanCafe.com. All
three services have similar approaches
to customer service, and each
successfully completed the orders I
placed, delivering scans and returning
the original materials to me in good
condition. However, the services did
have varying strengths and weaknesses
in the following areas: placing the
order, ongoing communication,
turnaround time, scan and retouching
quality, after-order support, and
pricing.
[...]
For ease of use and fast turnaround
time, it's hard to beat
ScanDigital.com, especially if you're
archiving 35mm slides. They
communicate well, provide free online
storage of your images, and generally
produce good output results. DigMyPics
is also a strong contender, especially
if you have lots of prints to scan,
and you want to review the results
online before making a final decision.
But if you want the best scans and are
willing to wait for them, then
ScanCafe is my recommended choice.
You may even be lucky enough to have a
local scanning service that you can
work with face to face. That would
certainly simplify using an outside
vendor and help easy any anxiety you
have about sending off one-of-a-kind
photographs. So be sure to also look
around locally when contemplating
options.
I also found a few recommendations online for ScanMyPhotos.com.