Focus – How to take pictures of many children so that everyone looks blurred?

I have Nikon D850 with AF portrait lens 105mm f / 1.4. I'm just learning to make good pictures, we buy this camera not for business, we have children and we want to make all possible memories. I'm using mode A, but often when I take a picture, one child's face is focused, another is blurred (I have twins, so I rarely get a good picture with both children focused). What configuration do I need to change? The birthday of the children is this weekend and I am the one who will take pictures of all the children.