One advantage of divorce mediation is that you and your ex get to propose your own rules regarding child custody. While your arrangement does still need to be signed off on by the court, this gives you far more freedom in determining how you want to move forward than letting the courts set the terms.
That said, experts warn against pushing too hard for too many rules. Make sure you really think through all of the potential ramifications.
For instance, perhaps your ex takes a very punishment-based approach to parenting. You want your child to have freedom to learn and make mistakes. If you do not find a balance, will you then regret it if the child is constantly in trouble and there is very little you can do?
Some parents also want to keep their own space from each other. They ask for rules that limit how much they can communicate. Your goal may be to keep your ex from overwhelming you with calls and texts about the kids. However, when you need to talk to your ex and your own rules make it impossible, it can make life more complicated for both of you and for the children.
This isn't to say you should not have rules. You just need to carefully consider what they're realistically going to mean in the future. Divorce mediation does give you a lot of power and the ability to craft the divorce agreement you really want. Take your time and go over every detail carefully, considering the future and your legal options.