Hi,
I'm the Gifted Youth Specialist for Mensa, and we have lots and lots for youth. I can absolutely promise we're not fading - we're growing!
You can find out about what we have to offer for kids here
http://www.us.mensa.org/learn/gifted-youth/, and what the Mensa Foundation offers kids here
http://mensaforkids.org/. Browse the parent/teacher resources there, and especially the Excellence in Reading program.
Like anything, people get out of Mensa what they put in. For some of our kids, it's the center of the social and intellectual life. For others, they just like the magazine, which, I would say is absolutely NOT boring - it's gone through a major renovation in the past few years, and it's really engaging.
In any event, I'm happy to answer any questions you may have. My email address is lisav@americanmensa.org.