In the hundreds of divorces that I have litigated, while there were plenty where one spouse used the children against the other, there were far more cases where a mother of young children was overwhelmed with fear an anxiety about not having the children in her company for any extended period. That's a natural feeling in them. It is something that they have to get over, but if it is the case in your sitch, you would benefit from finding a way to help resolve that anxiety.
Often, in any type of litigation there are "other" reasons that prevent a resolution from occurring and the parties are reluctant to even divulge those "other" reasons for fear of showing weakness or having it used against them. I remember mediating a mass tort case where we had reached an apparent impasse. The impasse had nothing to do with the cases before us at the time. The defendants were afraid to commit too much money to the claims we were currently negotiating for fear of not having enough money to settle the rest of our claims. Once we solved that problem. We settled millions of dollars of cases in a few days.
Try to make sure you really know and understand the problem she has with visitation and try to resolve it. You can "take" visitation by court order, but the resistance and undermining may still remain. If you can demilitarize the issue, you will have much more success. Of course, if you can't, you need to do what you need to do.
