Check out
http://www.felljunior.org.uk which has been running for about 9/10 years with the objective of supporting junior fell running. It originally hosted BOFRA and Kendal Series info as well until they got their own sites up and running. There was also a junior race calendar, which has now been replaced by the extract on the FRA site. Instead, there are now links to these new resources.
It attempts to complement this site, mainly by providing the junior championship points tables. However, it does not host a forum for the very reasons being discussed in this thread. I don't have either the computing resources or time/inclination/patience to moderate.
Ultimately though the means don't matter, it is more important to ensure junior fell running continues to prosper.