good point. Some of them are really antiquated. ...
There are approximately 1,000 of these and while many are of deceased family members there are also a good number of landscapes, cityscapes, etc. So, a gallery could be an option.
No Marburg, a gallery should be THE option. I suggest you take some digital shots of every single one of them, to have some backup in case of loss . then make a slide show with something like Ppt.
Then hit the pavement to go to galleries, public libraries,etc...
Even your local , provincial or even national art grants society.
As a big fan of archives, I wouldn't even bother with microstock.
This collection deserves more than that. If you can even gather some
of the original equipment, ie. view camera, glass negs,etc...
this would make the exhibition even more interesting.
Research with someone who is knowledgeable of photo history,
and team up with a good speaker.
You got something good there. Aim higher. Good luck