I am so sorry for your loss.
Not only is it normal to have hormonal issues (after all, some women even lactate!) but you are also going through intense GRIEF! Then, you have the added stress of trying to hide that grief and "come up with reasons" to your children about why you are so sad.
So you are hormonal, grieving, AND stressed, AND trying to bottle it all up and hide it! You need support, TLC, coddling. :( Yet we are always supposed to be superwomen.
I don't have a whole lot of advice.
Be sure to take care of yourself nutritionally! Like a marathon runner needs extra nutrients for the long-haul, you need extra nutrition (not extra calories - extra nutrients) to replenish all your neurohormones.
You need a person, or people, you can talk to about this. It is normal to grieve. It is normal to be hormonal.
It is critical that you get all the good-quality sleep you need. Make this a low-stress holiday season. Say "no". The world won't end if you do less and opt out.
It actually may help to just go ahead and let your children know (I don't know their ages) that you are sad sad sad. I once tried to hide something major and kids are smart. They know something is up and their imagination can be worse than the truth. There are ways to frame the truth that is reassuring to the children.