First, arrange for her your wife to be able to get as much sleep as she needs. Have family members or friends come help out, and consider hiring a night nurse. Sleep is the single best antidote to postpartum depression. Giving birth and ending pregnancy induce major bodily and physiological stresses. Sleep enables the body and the psyche to recover, healing themselves.
Second, check out the 3P's technique that I demonstrate in videos on my several websites (watchpsychotherapy and also prescriptionswithoutpills). I explain it also in my TEDx talk on lifting depression without pills.
You can do the 3P's technique with your wife, or arrange for her do it with a psychotherapist. The technique addresses whatever triggered the depression. When you have found a solution to that dilemma, the postpartum depression generally lifts, provided that the woman is getting enough sleep as well.
Lastly, if the depression still persists, explore getting a prescription for antidepressant medication from a physician.
The key: aim for prevention of hyper-emotional episodes rather than either a total cure (unlikely) or just managing the symptoms. Learn factors that keep the episodes at bay, factors like for instance getting plenty of rest and solving problems rather than letting them fester. Learn also to recognize the earliest signs that an episode is beginning; responding early on makes treatment most effective.
You can think of your son's fears either as a form of ptsd, or as an allergy to the dark. Shop around. If there's no energy therapist in your area, many work via phone or skype so you can find one anywhere.
The question then is what to do next. Best is to find out what has triggered the depression. What does your father feel discouraged about? Is there a way to help him get what he is depressed about not getting?
Medication for depression may help as well.
At the same time, loss of appetite also can stem from medical problems. Be sure to evaluate them as well.
For more information on helping someone with depression, see my youtube TEDx talk on lifting depression and my book, Prescriptions Without Pills: For Relief From Depression, Anger, Anxiety and More.
Susan Heitler, PhD