Multisite or Not?

So I cant point to a URL because I am deciding which direction to go.

I will give you a scenario and I could use your input: The Johnson family wants some blogs.

They want JohnsonFamily.com/Tim to be a branded blog for the dad.
They want JohnsonFamily.com/Donna to be a branded blog for the Mom.
They want JohnsonFamily.com/Joey to be the sons blog.
They want JohnsonFamily.com/Sue to be the daughters blog.

However, they want JohnsonFamily.com to be a branded blog for the entire family and show the most recent posts from all four blogs, as well as search through those blogs, catagories, etc… The reason this is tricky is because for any of Tims posts, etc.. they should all have Tims branding on it (menu etc…) even if the person comes from the main hub. So I have one of two obstacles to overcome…

I could put them all in one wordpres, but then I need to find a way so that the menu that look of the page changes based upon the catagory of the blog entry / or the blog entry itself.

Or I go wordpress multisite, but then how do I pull all the content into the main hub and make it searchable, etc… and link it back to the original posts? Thanks