As a teacher who worked with young children for almost twenty-five years, I found that one of the best ways to help the children focus was with Yoga. The atmosphere of a hectic classroom would become calm and relaxed within just a few minutes, and the children loved it!
For a parent, it can be a day saver! There is such wonderful value in helping them to learn how to stretch their bodies to release tension and to sit quietly, to calm their minds and bodies. The poses help their bodies become strong, balanced, and flexible; and they look so cute doing them!
Meditation can be an elusive thing for most adults, but just learning to sit still quietly can be challenging for many children. Shambala Publications has a book called, "Sitting Still Like a Frog" by Eline Snel, which is a great introduction to the basics of mindfulness for children in a fun, easy to understand way.
Gaiam has an excellent selection of yoga mats, balance balls, balance cushions and other yoga accessories for children. You can see this colorful selection here.
Yoga is a valuable practise for adults, too, so why not join your children? It's a great way to bond and you will help them to cultivate a healthful, lifelong practice.