Children are resilient, but going through their parents' divorce can really shake them. This scary time should be a time when they can count on their parents for support. The problem that sometimes comes up is that their parents might be so involved in the divorce process that they are unable to give the children the attention they deserve.
When you are trying to help your children through this time of transition, remember that everything they've known their whole life is changing. You know what life was like before you got married, but they might not. You should be prepared to discuss what's coming with them.
The feelings that your children experience in these cases can vary greatly. Sometimes, they might feel like they are the reason for the divorce. They might push against having to make the necessary changes. You will have to reassure them that this wasn't their fault and that being willing to be adaptable will help them out.
Since your children will be spending time at both homes during this transition, you should work with your ex to find out how everyone can make things easier for the children. You have a long parenting relationship to work through with your ex so being sure that you are setting the situation up to be as easy as possible can help you in the future.
As you work through the divorce, remember that your children have to be the focus on the child custody agreement. This must be set up to reflect the child's needs now. You can always work on a modification later since your child's needs will change as they grow.