Often when a child has anxiety, parents feel a sense of helplessness. If you feel overwhelmed, please check out the Limbic System and The Daily Program. You can practice the breathing and Qi-Gong with your children.
Understanding emotional dysregulation can help parents and children.
Here is a link to a series of videos that help manage small Children in Distress.
http://anxietycanada.com/MindShift-CBT
Understanding Eating Disorders in Adolescence
Complex trauma and PTSD in children
There are also books – Taking charge of ADHD by Russel Barkley
Recommended books for children:
Books for parents with children with anxiety.
Taking charge of ADHD by Russel Barkley
Freeing your child from OCD by Tamar Chansky