I didn't look too deeply, and of course valid feedback depends on the age range of your target bloggers, but get away from words like "utilize". I tend to not associate understanding and embracing that word with 'kids' ya know?

As to how to get kids to sign up and use it: first provide the registration link each time you say "register" or "registered" so's it's right there in front of them. Next create a sandbox blog and a howto blog. Give each blogger permission to post 'protected' only in that blog, and let them play with it. Make it clear the sandbox gets cleaned out from time to time and the howto gets followed by you, and make sure to follow up with questions in the howto blog. When one of your registrants gets the idea and digs on it they'll start blogging. If the point of your application is worthy then more will follow. If not, well, you delete it all and go back to the drawing board...

BTW I'm about to unleash a similar application, only mine is for people old enough to learn all they needed back when teevees had rotary selector switches on them. I think my application is worthy, so I've editted all the default posts to be howto posts, and will give each of these old farts permission to post in the sandbox. I'm also installing a phpbb forum for them cuz some of them know 'new things' like how to play in a forum...

Email. Blech. If there is a way to email the world that a blog exists I don't know about it. RSS, and I sort of figure kids are hip to what that means. Their parents might not know, but the next generation is a lot smarter online than the current or previous one eh?