Do what you feel you need to do, OP, and don't feel pressured to do what doesn't feel right to you. There is no right or wrong here - just what feels right to you.
I am a very private person. When I read the post about the nanny not mentioning that her mother had passed away, I understood it completely. As a nanny, I love my employers children and I work in their home. They do not love my children nor have ever met them and they have never been to my home. While I like and respect the couple I work for, I don't love them and we aren't "friends". If I were in your position, OP, I would never mention my loss to my employers but I would hug my charges tightly and tell them how much I do love them on Monday morning.
I am so sorry for you loss and the pain you are experiencing.