As a formerly lifelong morbidly obese person I have to say this...

Let the kids have their fucking chocolate milk... give them vegetables and fruits and lots of protein and see that they get lots of water and a little juice...  take away the video games, give them a stick and send them outside to play... make sure they are well socialized and emotionally healthy... play with them, love them, and pay particular attention to the first 3 years of their life... but take my word for it, a container of chocolate milk with their school lunch isn't what makes them fat and unhealthy... that comes from being unsocialized, inactive, withdrawn, and introverted...  aka being lonely and generally unhappy...  poor eating habits can be supplimented and turned around, but I truly believe (through personal experience and observation) that the root causes of childhood obesity are emotional and not dietary.

Let me also add... make sure your Dr is looking at EVERY medical possibility for unhealthy weight issues... Polycystic Ovarian Syndrome in little girls is a huge cause of childhood obesity but until very recently that wasn't a disorder that was even thought about unless a woman had serious issues with cysts or had difficulty getting pregnant.  It is caused by an imbalance with insulin/glucose and even if all the tests for diabetes and other insulin/sugar related disorders are negative make sure that the ratio between them is being looked at as well.  PCOS is a precursor to adult onset diabetes and can contribute not only to weight issues but depression and other emotional issues as well.