Boys & Girls NI
This is a starting point for the idea you have in mind here a 2 mock examples of how you can share and restrict access to registered members
There are ways to protect the individual files but unless it is sensitive material it is probably best not to, it will mean all the young people have to remember the login I think you should try it first by not hiding but not telling the out side world about it.
The zone can have it’s it it owns blog, below is existing but the idea I have is to create an article for each interest/topic/file and show it in a grid below.
So you will have a site with a site, regarding protecting the files this can be done but let us try without first