As a father who is married, I would approach any issues that I was having with my child or children from a unified front. I would speak with my wife and we would decide how we would talk to the children about the issue at hand, whether it be watching too much TV or ditching school. I think if we were to each talk to them separately, we might send mixed signals. Talk to your partner, tell then how you feel about it. Maybe they will feel differently about it and can convince you to feel differently. Then you approach your child.