The course should be first and foremost RELEVANT to kids. Computers are best taught practically, and kids spend pretty much all their time on port 80. Start with the things they like and work backwards, not from bits and transistors upwards. "y'all like facebook? Here's how it works. There's a server somewhere and it talks to your computer. I've got a server here; let me show you how to power it up, start apache, type "boobies" into index.html, have it show up on everybody's laptop when you go to 192.168.1.142."
"But what if you want to make the page change? Then there's php." Show them a few scripts. Have a drupal installation to manage the course pages. Give them accounts with admin privileges over some section of the site and have them manage it.
From there move on to how apache interacts with the OS, some hints about C, hard drives, things like that. Have them tear apart some old computes, or maybe even build a classroom server from parts.
Make it FUN.