Good idea. Then un-plug the ethernet cable and tell them that the cable represents the internet. Or put a switch in-line and power down the switch and watch as the network connection is not available anymore.

Bring a few 48-port switches or something else in that's big hardware that they can ooh and ahh over. Better if they have lots of flashing lights and loud fans. If you're a Sysadmin, you should have access to a bunch of random hardware that you can use.