This is a very personal decision and varies from family to family.
Depending on the situation, it can be very difficult for all of your children to agree on every decision. Forcing them to agree can also mean forcing them to fight.
Also, appointing one or some of the children, but not all of them, can impose an unnecessary burden on them and lead to further conflict. A better option may be to appoint an independent uncle or aunt or family friend and let them make the decisions.