Windows 7: maintenance on home networked PCs

I live in a small house with a few others who are now all my good friends. Unfortunately, none of them knows anything about computers more complicated than Facebook, which leaves me to manage everything by myself.

I have a pretty nice setup going, and by pretty nice I mean it works
The only major downside is the time I spend keeping up on maintenance on all six or so machines in the house. While most people are content to just have everything autoupdate, I find that it slows all the computers down considerably, most notably immediately after start-up. I have been manually updating everything (Firefox, java, Windows 7 updates, misc software, etc...) which is fine. But my problem comes when I have to do it on each machine. Repeating the same update six times or so is monotonous, and I start to lose track of which ones have gotten which updates.

What I would like to know is this: Is there a way to have it so that I only need to update one central location to update all six separate PCs?
All are running Windows 7 SP1, mix of laptops and desktops from different manufacturers.

It would involve setting up a server and turning your home into a domain, which would create far more work.

Honestly, the best option is simple education. If a person can't be bothered to run Windows Update and pay attention to system tray icons, then tell them you won't be responsible or available to fix their computers.