Don't overload them with information. Children can be fearful about death and the future. Don't offer false comfort. Give them a chance to talk about their fears and validate their feelings. Offer a simple expression of sorrow and take time to listen.
Children are repetitive in their grief.
Respond patiently to their uncertainty and concerns. It can take a long time to recover from a loss. Children are physical in their grief. Children grieve cyclically. Expect their grief to revisit in cycles throughout their childhood or adolescence.