See how each child is behaving. Don't rush in with explanations. Usually, it's more helpful to ask exploring questions than to give quick answers. When someone loved dies, don't expect children's reactions to be obvious and immediate. Be patient and available.
Children are part of the family, too.
And reassurance comes from the presence of loving people. Children feel secure in the care of gentle arms and tenderness. When describing the death of someone loved to a child, use simple and direct language. Express your own feelings regarding the death. By doing so, children have a model for expressing their own feelings.