Micro-site within Main Site

Hello, I'm looking to create several micro-sites within my main site. Each of these micro-sites will use the same theme as the main site, but will have minor differences. Each will be co-branded and some custom content. So, there would be each company's logo on their pages, and some content relative to only them.

Each mini site would probably have its own URL or sub-domain (CNAME) so we could direct each company's users to their mini-site.

I have looked at several of the plugins here at MPMUDEV, but I'm still not clear on the best direction to go with this. Does anyone have a suggestion on how best to accomplish what I need to do?

Thank you for your time!