I don’t know of a website with tools for kids to keep food and activity logs, but you can assess pediatric BMI and calculate her calorie requirements with the Guide to Pediatrics at About.com   Children and teens can learn about weight control and other health topics at the Kids Health website.  Parental training is another important part of pediatric obesity treatment because parents must take control of the home environment, stick to a structured reinforcement system and use behavior-change strategies that emphasize praise and unconditional acceptance.  Read Your Child's Weight: Helping without Harming by Ellen Satter to learn how.