None of my plans are set in stone yet, but my general plan is to make the course as interactive and fun as possible. There was a thread recently[0] discussing Robotopia, which I like the premise behind. I'm not sure if it's quite polished enough yet to be used. I'm heavily considering using either the offline or online version of Scratch[1] but don't know quite what direction I'd go with it. I also saw there are minecraft related programming lessons[2] which sounds really neat, but I haven't looked at this in depth yet.
Anyway, I could list more tools out there, but most importantly, hearing what has and hasn't worked well when working with kids would be great!
[0]: https://news.ycombinator.com/item?id=14043519
[1]: https://scratch.mit.edu/
[2]: https://code.org/minecraft