Given that Khan is hosted entirely on App Engine, I wouldn't count on a Node.js-specific tutorial series starting any time soon, but JavaScript in general is possible.
On the other hand, what the fuck do I know. I'm a Smalltalk developer leading a .NET front-end to a Python project.
We miss you, kamens. :(
And as someone noted, with Resig there, this is just a matter of time.
Javascript is great as intro. Kids are naturally drawn to shiny things and you can create plenty of shiny stuff with Javascript with minimal setup.
Once you hit the natural limit("how do I save the scores!"), you can move on to PHP/python etc.
JavaScript is great for me when friends ask me: "Hey you know programming right? Show me something on my computer" but if they want to learn programming, I'd just ask them to download Python or Ruby.