My son is a first grader at KIS, where they use iPads from a cart in the classroom. Santa had brought him an iPad mini for Christmas, and we have already been using it for him to be more organized for school. He uses it for recreation, and a bit for school related tasks.
I came across two apps, but Super Stretch became his favourite. It has pleasant animations, video clips of kids doing the poses, a reward system, and a code of ethics. My son decided that everyone in the house needed to do the Yoga, getting his little sister, Gran, Pop, Mom & Dad to join in.
Here is the AppStore link: