Coming up with the terms of the child custody agreement with your ex might be one of the points of the divorce that you are dreading. This doesn't have to be difficult if both adults are willing to work together to do what's best for the children. You can look into the parenting plan points that you need to work on. Take the time to review the possible arrangements so you know what's possible.
One of the first things that you need to determine is where your children will live. Even if you and your ex will split parenting time evenly, one home is going to be their primary residence. Once you know this, you can work out the parenting time schedule. This needs to be realistic, so base it on what both can reasonably do.
When you are setting up the parenting time schedule, don't forget to include special provisions for holidays. It might be helpful to jot down what each side of the family does for these days. For example, if your ex's family celebrates on Christmas Eve but your family does things on Christmas Day, letting the child spend time with the family who is celebrating might be beneficial to them.
When it is time to work out the details with your ex, go into the session with an open mind. Your ex might have options that are ideal for the situation that you didn't think of during your brainstorm session. Try to remain calm even if the discussion gets rather heated. Your only goal during the process is to do what's best for the children.