Do your children see two types of parents? When things go well do they see parents that are content and pleased that things are under control? However, when things enter the twilight zone of disobedience and chaos do they see parents who are upset and whose only focus is to get things back under control, no matter what it takes? Kindness seems out of place in this twilight zone. But if God's love for you is your model, kindness is always appropriate. Being kind does not mean you don't discipline or correct. It does not mean you roll over and give your kids control of the house. It does not mean lowering standards. Being kind means that you show God to your children. It means you follow God's good example that he is always kind and compassionate with you, even when he disciplines you.
Love is kind. You are trusting that God will provide his wisdom in difficult situations. You are demonstrating the extraordinary holiness of God by the way you act. Your words are pleasant. Your focus is clear. Your manner is kind. Yes, there are consequences for sin. But the consequences are administered in light of the gospel grace that has been given to you.