Good advice here coming from Divorce, it's just the beginning blog's We Assume a Rational World.
There are no quick fix answers to any of these questions. Each divorce in unique and a “one size fits all” answer doesn’t exist. Keeping this in mind, there are some things a parent can do to minimize the irresponsibility the other parent exhibits. My first suggestion is DON’T lie or cover for the other parent. The children are going to have to figure out their relationship with both parents and cannot do this if they are being presented with misinformation. The parent also should not highlight or dwell on the irresponsible behavior of the other parent by engaging in talking negatively about them.
Try to role model for your children the types of behaviors you want them to exhibit as they grow into adulthood. If you are yelling at them, you are teaching them to yell. If you complain all the time, you are teaching them to complain. Try to show your children the way you want them to act by modeling that behavior. If your ex-partner misses visitation, be there for your children to let them talk about how they feel while letting them know that a parent shouldn’t act that way.