What are some free kid-friendly tutorials to get started with Mindstorms Nxt 2.0?
You can find some free instructions at http://www.nxtprograms.com/ and at http://thenxtstep.blogspot.com/p/building-instructions.html. But I am not sure if you can say they are kid-friendly.

And here is another one:  http://legoengineering.com/curriculum-submenuteachingresources-142.html