cat has provided you with some very wise words about getting stuck into their routine. You do not want to be drawn down into the dark pit with them. It's so easy to fall into that pit with them because of the mood swings. Step back, allow them to wallow in that pit by themselves.
She's also correct in stating that they sleep a lot and then other times are higher than a kite. It's all part of the depression. The depression self medication can be in the form of drugs, booze, women, gambling, internet, porn, sports, eating, sitting and staring into space (or as I say, zoning out), anger, etc. That is why it is very, very important to keep the focus on you and your children. There is nothing you can do for them.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.