Being a Certified or Registered Clinical Counsellor is not enough, at least five years of related experience is recommended.
Gaining experience as a Child Counsellor before transitioning to a therapist for children of divorce will greatly benefit you.
Take special training in how to work with children of divorce. There are many online resources which can help but consider finding someone to mentor you as they can guide you through the learning process and help you better understand parenting time and the judicial process far better than any online course or textbook can.
It's a very different kind of therapy. Children of divorce can get very distressed, very angry, they may make up stories, they may be coached by one parent to make false disclosures of abuse against the other parent, they may be alienated by one parent against the other, they may be pressured by one parent or both, they may be put in the middle, they may act out a parent's anxiety refusing visitation with the other parent, they may manipulate trying to save one parent's custody interests, they may state being afraid of one parent when actually they are not. etc.
Custody fights are ugly and fierce. You can't just believe everything you hear from the child and the one parent who brings the child to you. You must hear the other parent's story, too. Serious accusations fly on both sides. You may have to be a bit of a detective and sort through the information before you act on it or put it in the report.
You will likely be asked to write a report or letter for court. This is a very high responsibility, because it has very deep and long-lasting effects on the whole family. Imagine you are given untrue information by the child or one of the parents, you believe it and put it in the report like it's a true fact. Then the child's relationship with one of the parents is wrongly limited or severed for life. Can you live with that? What would you do if someone did that to you and you lost access to your child? Would it comfort you to know that they sincerely believed what they wrote against you in the report or letter to court? Would that be enough for you, to lose access to your child over it?
The wronged parent (and sometimes even without being wronged) can sue you for many things: for being unexperienced for child's age and/or divorce/custody issues, for not obtaining both parents' consent before doing therapy with the child, for making untrue allegations about them, for alienating the child from them, for harming the child's trust in them, etc.
Counselling children and parents during highly conflicted custody process is not for the faint at heart. No matter how professional, ethical and objective you are, parents will be unhappy and accuse you of being biased, unethical, and unprofessional.
Can you take the criticism of parents and lawyers? Can you accept that your character, ethics, professionalism, and work may be scrutinized in court?