If you want to win at custody without being a Mom, your first step is to step up your parenting. What does that mean? It's simple, it means doing all the things that Moms traditionally do like making doctor's appointments and talking to teachers.
You should also seize your rights. Contact the schools and daycare centers that your children attend and ask for all records to be shared with you. You are a parent, don't wait for your ex to share with you, take charge.
Ask for what you want. If you want joint custody, tell her. If you want Monday and Tuesday nights, ask for it. Do it in writing if necessary so that you have a record of our requests.
Go to court sooner rather than later. If you can't work things out, don't wait. The sooner you file for custody, the sooner you will have a resolution. But, if you are not familiar with the court process, you MUST hire a lawyer.
Fathers can win custody by following the right strategies. Good luck.