What tools should i teach?
Foot print......................Nmap,

Vulnerability..................Nessus,

password crack.............John the ripper,

sniffers..........................ettercap.

Although, I think the prinsciples, rather than the tools, are more important.

What "sample" O.S/Config? Net equipments too (routers, swtiches?)
What ever you use needs to work straight out off the box. You do not want to spend half the lesson configuering the network, although, that! in it's self, may be a valuable first lesson??.

Which live CD do you recommend?
The fastest, I wish I could help you here. I'm only familiar with Knoppix STD