I went through this a few years ago. In my state (Massachusetts) part of the divorce process comes up with filing a "parenting plan" with the court. This is a legal document that includes legal and physical custody, who makes medical decisions, whether the children can be moved out of state, religious issues... and anything else that is important to you and/or the father.
There are three ways to come up with a parenting plan.
One is to sit down with the father and negotiate the important issues, civilly. This involves give and take and the ability to talk to each other with respect (not always easy during a divorce).
The second way is to get lawyers and to have the lawyers negotiate the important issues. Your lawyer will represent you, listen to what you want and explain to you what is realistic. The father's lawyer likewise will represent him. The lawyers will tell each of you what would likely happen if it went to court, and hopefully you will reach an agreement.
The third way is to fight it out in court. In Massachusetts they make it very clear that judges don't want to hear your case, and that if the judge thinks you are the one being unreasonable, they will rule against you any way they can.
The first way is often impossible because of the feelings in divorce. The mother of my children and I tried to hire a mediator... but this broke down.
The second way worked well... the lawyer told me what he thought was reasonable, and I had to back down on some of the things I wanted, and I got the most important thing for me (which was shared custody). This worked for us because the lawyers shielded us from the emotions of the divorce (we weren't directly fighting each other). The system worked.
I don't recommend fighting it out in court. This is a good way to pressure both you and the father into being reasonable with each other, but it isn't ever a threat you want to have to use. It isn't good for you, for him or for your children.
I chose a lawyer who would be reasonable and negotiate what was fair... I didn't go in to these negotiations looking for a fight or to punish my ex-wife. I highly recommend recognizing that this is a negotiation process and things are best for everyone if both sides can be reasonable.
I hope that is helpful.... my original advice stands, the first step is to talk to a lawyer.