If the small museum is run by volunteers with a tiny budget as ours is,  our
experience might be helpful.    In a historic building without climate
control, we need to mount photos which will not warp due to humidity.    We
(volunteers) wet-mount photo enlargements up to about 18 by 20 on Masonite,
cut to size by another volunteer.  (18 x 20 is tricky and takes experience;
11 x 14 and under is easiest).  When the photos dry, we spray with matte
finish.   This works with conventional black and white or color prints, but
not with photos copied with the digital or electronic process.  They melt
like the Wicked Witch of the West--the image just runs off the paper.
I'd encourage them to get good 4x5 negatives made; they will remain in their
collection and can be reproduced for years to come.
Mary Prendergast
Harding Twp. Historical Society, New Vernon, NJ