It's best to avoid the attitude of "how can I end up paying the least" as much as it is best for her to avoid "how can i get the most". What do the children need? Do your best to see that they have it. It's what you're doing now, and if you stop doing it because of the divorce then you will be hurting the children to get at their mother or to keep money out of her hands. Most important thing: they have a happy childhood.