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.