Having Several (Many) People Add Thier Own Content

What I want to do is put up a web site to help mark my mother’s 80th birthday (in December). I’ll use it to let people know about a family party but mostly, want family and friends to add content easily.

Do you think I should use a Directory plug-in or maybe there’s a better option. I’m fine with a site where I am admin and have another one or two contributors but all I need here is for say a half dozen people to be able to post without access to *only* the posts they might create.

Thanks

Martin