Toddlers will be old enough to sense changes in their environments. Since they spend most of their days with at least one parent, it's important not to neglect them. Otherwise, when they see the house in disarray and gradually getting emptier, they may worry about being left behind. Quickly allay their fears by keeping their favorite toys around and trying to keep as stable a household as you can during the planning and packing. As long as toddlers are comfortable and are close to their parents, they will not be affected by the move.
Let him pack and tote along some of his special possessions (do not discard any of them before the move, no matter how old and tattered they are).
Elementary school children have developed relationships with people outside of their homes. Leaving their friends will be difficult but the idea of moving to a different place can be exciting.
Since school is the primary place where children make friends, children in this age-range tend to have the easiest time making friends. They spend most of their time in school with the same classmates and the same teacher. Relationships develop naturally.
Children in this age-range should also be active participants in the move. Allow them to pack their own belongings. Teach them your new address and phone numbers right away. After the move, take the time to show them around their new neighborhood.