Hmmm, a wiki and a blog serve really quite different purposes. I don't think that a wiki would fir the OP's stated requirements. The OP wants something to share ideas, news and information with a groupe of people, so a blog or a mini forum is what is needed, a wiki is more for working collectively on a group of documents to improve them progressively together.

Well, Oddmuse is a Wiki written in Perl, and it can be configured as a blog with categories.
As it requires basic (hmm, not too basic...) knowledge about webserver config :-) maybe it's not exactly what the OP looks for, but I think it might come near.

I have to disagree; a good wiki can selectively give write access to a limited number of users (or just the owner) and thus meet all of the OP's requirements.