Getting from zero to fun as fast as possible is key. Open up the DOM tools, show them a couple things, and step back. Be attentive to questions, encourage students to share their discoveries. Show them the console and how to show a prompt, alert, console.log, and set variables. Make a simple script and email it to them to paste into their console to do something fun, like add a CSS spin animation to images. The ones most interested will explore why it works and their curiosity will be the engine of their own learning.