I handle a couple of American public television station websites (hence my nickname) and do a lot of things specifically geared toward schools, educators, and students. However, I also preach Internet safety for kids, and what you're proposing, although easily done, doesn't sound very safe. When children get on the Internet and are identified as such, they become open targets to a lot of sick people.
If you're really going to go ahead with this, then take some serious precautions. (These may be pretty obvious to you, but I'm just making sure that they're posted with this thread for anyone else who may try this.)
- Don't use any real names or personally identifiable information.
- Don't allow comments.
- If you must allow comments, make them moderated and require approval, and only give moderation password access to a responsible adult.
- Post the fact that these blogs are adult-moderated irregardless of whether you allow comments or not.
As great a medium as this is for teaching, it's also a perfect place for lurking. I don't think that we should scare kids away from it, but we have a responsibility to teach them the realities of it as well. Exchanging seemingly personal comments and a few jokes with people over the Internet, doesn't mean that you know them or can trust them. It's just that kind of world.