I think the best support a child can get is not from a counselor or a therapist, but from their parents. I honestly believe that I cope so well with my PKU, because of my parents neverending positive attitudes. They raised me to believe that I was no different then any other child, because I wasn't, and that is what I grew up believing. I treat PKU as nothing more than another part of my life, because that is how my parents always viewed PKU. I can tell you from a personal perspective that PKU has never hindered me. In fact it's probably given me more strength, self discipline, and a positive outlook in life.
Keep doing what you guys are doing. I'm sure your little ones will be just fine. They're in great hands :).