Your divorce is a difficult time for your children. They might internalize the matters that are going on right now. As the parent, you have to determine how you might be able to help them through this. One of the most important things to do is to remind them that they aren't the cause of the divorce. No matter what happened that led to the divorce, you can't try to push the blame off on the children.
For many children, the negativity of their parents starts to infect them. This is a tragic situation because the kids might miss the beauty of the fresh start. This is an area that you and your ex might be able to help the children.
Instead of focusing on divorce as a negative event, you need to think about it as a positive life event. Yes, it is hard to say goodbye to the marriage that you thought would last forever, but now is the time that you can reinvent your life to reflect your current wishes.
Trying to keep the positivity with your children can be complex because children have such raw emotions. You might try starting some new traditions with them so that they have something to look forward to. These don't have to be anything huge. Maybe you can grab pizza or make nachos and have an at-home movie night the first night they are with you after spending time with your ex.
Another necessary step is to encourage them to continue on with relationships with extended family members. This can add to the stability they feel so that they can see that even though a good portion of life has changed, there are still some constants that remain present.
Your parenting plan should also provide stability for the children. Most parents try to come up with the terms as soon as possible so that everything is in writing.