When you have children with someone, you are going to have to deal with that person for a long time, at least until the kids are grown. If you divorce, this can be a challenge since you will have to continue to act as a parenting team. This can help to head off issues that can occur when the kids try to play one parent against the other.
Children are often very perceptive and observant. They are good at figuring out which parent they can get to agree to specific things. Once they learn this, they might use that knowledge to get what they want from the parent who will agree. This may not be a huge deal in some cases, but there might be times when they go to one parent after the other one has already given an answer. This can cause tension in the parenting relationship.
Having good communication with your ex can help you to learn when this is going on. Be willing to speak openly about the kids. Discuss the things that you've agreed to and the things you've said "no" to. Both parents should be willing to back up the other parent in front of the children. If you don't agree with what your ex decided, discuss that when the kids aren't around.
You should also make it clear to the children that playing one parent against the other will come with consequences. Setting these expectations early can be beneficial for everyone. If you and your ex can discuss this with the children together, it might make more of an impact.