Should references in foreign language be translated to make popular audience get familiar with how academia works?
Figure out what the younger portion of your target audience is, and find out how comfortable they'll be with the various languages your references and quotes are in.  For example, my guess would be that your typical younger readers would be age 12?  And that you are writing in German?  I imagine your interested 12yo readers will be okay with most article titles given in English, so those translations could be given in footnotes.  The reader who doesn't need the translation could just keep reading and not bother with the footnote.  My guess is that all the French would need to be translated.

The general answer is, you need to know your audience.  Give some talks in schools to get to know them better.