Find something to take apart. A medium sized machine. Perhaps something you don't need to put together again. It should be "clean" so there's no need for extensive cleanup. This would be a good time to introduce safety glasses and gloves.
In general, think of the things your team does during the year and try to represent them all in your pitch. Be sure to introduce GP and the mantra that goes "It's not about the robot."
Oh, yes, and be very, very sure to ask them what they would like to do on the team. Ideas are precious and delicate in their infancy. Make sure they all get a decent chance to thrive.