Thanks all for the replies!
I do feel like I should get some $ out of it, cause there is no exposure or publicity to get from such things.
The only 'donation' I do, is like for my first clients, she bought 2 pictures (50$ for one and 30 $ for the second.
I put them on a cd and also included the other decent pictures that were not good enough to my own standards (I would not have sold them anyways, but they are not bad enough to ruin my rep).
Client was super happy. She also wanted the 2 pictures she bought, with a black and white version, which I included for free also, as well as 'miniatures' that she could easily send via e-mail or use on FB.
I'll try to find her website with hopes that she includes prices to her work...