Depending on your time limit...
If that were me I'd get a little inspiration from beginner bass instruction videos, provided I know what I'm talking about...Your speech will come much more naturally if you know what you're talking about (i.e. you're not going to go off trying to demonstrate a 12 Bar Blues if you're not familiar with what it is). Most instruction videos begin with showing you the parts of the bass then go on to simple theory or maybe a simple bassline.
I'd start with a little history of the bass, then go on with showing the parts of the bass, etc. Maybe a tiny bit of theory, a scale or two, how a song comes together...And do what you can to hold the other students' interest. They may not be musicians themselves so I would say this is the time to do something that would make them go "ooooh ahhhh", like playing a bassline you know. The students may care less about learning the instrument, but they want to be entertained...and maybe develop an interest in the bass.
Good luck.
but hey its all good
