You could try a printing on demand service like this to reduce costs? Perhaps invite your community of learners service users to co-create cards, photograph artwork then put on cards! - so order only what service users want and go from there! with a trackable link (on the back of the card) you could get the postcard to sell itself ;-)
Postcard Printing, Post Cards, Custom Postcards, Create a post card
In-kind advertising for non-profit organizations
Google Grants is a unique in-kind donation program awarding free AdWords advertising to select charitable organizations. We support organizations sharing our philosophy of community service to help the world in areas such as science and technology, education, global public health, the environment, youth advocacy, and the arts.
more stuff like this in our diigo groups...
Charity Chums
http://bit.ly/2J4Gx
Accelerated Family Learning - Friends of Campaign4 Learning
http://bit.ly/gMmKx
alternatively...
...much more stuff on my twitter stream...
catch more posts like these and others on socialmedia, emotional intelligencde, persuasion, collaboration & the arts on my twitter stream...
@williamdoust