Lexie-
I am so sorry for the situation as a whole.
There is a fantastic ED clinic in the metro area I think your son/family resides in. It is very well respected both on an inpatient and outpatient basis and I suspect/know from friends that have had treatment there that family work is a part of it.
A book I have found really helpful in my own recovery is Eating in the Light of the Moon by Anita Johnson. I also recommend it to loved ones trying to get a handle on why their loved one may "do what they do."
Sending warm, loving thoughts to the universe for your loved ones today.