The books we've made through Blurb look high quality to me. They offer several choices for the type of paper at different price points, but I didn't do any research on that. We went with Blurb because it has some relationship with Flickr for pricing and an interface to import our photos from those already organized albums (see "Prints" from the drop-down menu on Flickr). It used to have a decent web app for creating a book. Now you have to download and install their Windows-only desktop app, but it's good.
If you are making a book for your mom, pay for the higher quality options if offered, such as hardback with a dust cover over paperback, and the heavier paper if offered.
The U.S. Library of Congress recommends acid-free paper for archival storage (https://www.loc.gov/preservation/resources/rt/perm/pp_x1.htm...) but AFAIK this option is not available for commercial photo books.
My next questions were then how do you arrange a project for the intended audience (context and information is important as random photos of people 100 years from now won't have much value). And then how do you create it so the paper book lasts for 100 + years.
Your idea on Blurb was was interesting to me. Do you know the quality of the paper of the book will survive a long time or did you look into that? Also what reasons did you settle on Blurb (if you don't mind me asking)?
Thanks for pointing me in the right direction - I was about to suggest printing out individual copies and putting them in classic photograph book with plastic covers and adding her own blurbs.