Ketogenic diet has been used for epileptic children for a long time, and studies do show it helps with their condition. On that note, you would need to work with a doctor or health practitioner to make this work. It's one thing for someone to go on a ketogenic diet and get tired, ect... but were talking about an epileptic child going on it.
"The Ketogenic Diet" by Lyle McDonald is the best guide I've seen on ketosis, and many studies in the book are the ones based on epileptic children. He states in the book as I said above, get a doctor's approval and advising.