Have you considered documenting the project?

"Leider geil" ("Unfortunately awesome") is a song by German band Deichkind. If your project is unfortunately awesome, document it and let others know. Photo by Katharina Weber
For NGOs: Get the appropriate credentials from the festival (e.g., a photo pass), and then take lots of pictures and videos (but please respect laws and personal rights!), so you are later able to document and evaluate your project. Talk to participants and your members and write down their feedback.

Careful: You will likely need a photo pass to take pictures with a professional camera anywhere on site. It never hurts to ask the festival for guidance when it comes to taking photos. What are their rules?

Maybe an official festival photographer can assist you with taking photos.

For festivals: Send an official festival photographer to take pictures of the NGOs and their activities. You might use the images for internal documentation and/or turn it into a news release. It’s also nice to allow the NGOs to use some pictures free of charge, since they might not have professional camera equipment, and they might also be too busy with their projects during the festival to take pictures.

Here’s an example of a great introduction to a project of Roskilde Festival, “Orange Together – exploring lols, lust, love & limits” in video form (Danish): 

This project has been funded with support from the European Commission. The author is solely responsible for this publication (communication) and the Commission accepts no responsibility for any use may be made of the information contained therein. In compliance of the new GDPR framework, please note that the Partnership will only process your personal data in the sole interest and purpose of the project and without any prejudice to your rights.