Now, I'm personally more of a pilates girl myself. I've never found much solace in an actual yoga class. But I do think I know enough to be able to demonstrate. I think too, it may help with those kids who just don't know how to relax. I can't imagine being so stressed and angry at age 5, but I see that in more and more students every year. Maybe particularly the breathing techniques will help a child be able to calm down.
I found this resource that I might invest in, I particularly like the poster: http://www.abcyogaforkids.com/
This book looked good too.
Blogs about using yoga in the classroom: http://yogainmyschool.com/ and http://omazingkidsllc.com/
Some ideas to use it with literature: http://pinterest.com/yogainmyschool/books-for-kids-yoga/ (love the Brown Bear, Brown Bear idea).
And of course, lots of youtube tutorials:
Does anyone already use yoga with their kids? Does it help?