My mom told us to pack some things, that we were going to the beach. We drove and drove and finally got to my grandmother's house. We were really scared. My parents told me as soon as it was definite. Whatever parents are able to do to eliminate trauma in a move is advisable.
Children can deal with a move if they are dealt with honestly.
A move always brings a certain amount of anxiety for a family. Even if the children are in favor of the decision completely, there are still unknowns and questions which will need to be answered as truthfully as possible. Children, as do adults need time to deal with feelings of loss or separation. The more time they have, the better. Tell them as soon as you are able.