Moving to a new city is a completely different experience for children than it is for adults. While the parents usually have an idea of where they are moving and what they are getting into, kids do not. However, what kids do understand is that they are going to be losing all their friends (and their friends are just as important to them as your friends are to you, maybe even more so) and going to a new school of which they know nothing. It can be aa scary and intimidating experience, specially for a shy child. To make things easier for your children, many parents recommend to wait till the summer break to move. This will give your child enough time to acclimate to a new home and a new neighborhood.
Before choosing a new home, you may even want to take the kids along when you visit your prospective new neighborhood. If you can't take all your children, try to take at least one who can be the spokesman when you return. His/her siblings will most likely believe that he/she is telling the truth more than they believe you.
Be positive. Moving with your children should be an adventure. Although moving may be good or bad, you at least have a say in the matter; they don't. Give them a break, don't lay more anxiety on them. Every new city has something positive about it, so emphasize that. For example, with free access to the zoo and the Smithsonian museums, there are a lot of activities that a family with young children can do. Although mentioning the fun facts is important, don't deny the undesirable aspects, admit to them but talk about the good stuff. Try to think what you would like to hear if you were a child. Think with your heart instead of your head.
The younger the child, the easier the transition will be. Just keep the feeding and changing routine for the infant and they will be fine, whereas your teenagers are going to be unhappy no matter what you do. Get them involved in the move, in the discussions, and in the decision making. Recognize them as individuals, but they must recognize you as authority. It does not have to be equal responsibility to still be fair.
Do a walk-through with your younger kids the first day of school. Visit all their classrooms, see their cafeteria and their shops, so you can respond when they come home with their tales of woe. Be sure they know you are all in this together.
Encourage your children to bring their new friends over as they meet them and assist them in staying in contact with some of their previous friends. In other words, be good parents. One role of a good parent might be to plan family outings in your new environment so all of you can explore together.