First, I would like to gently point out that you owe her the money regardless of visitation. That is money for your kids, so pay it on time and let go of any connection you have between that and visitation.
Was there any way to arrange an alternate schedule instead of less? Let's say you had the standard e/o weekend and weds evenings. If you worked late on weds, for example, you can arrange whatever day you want, as long as the ex agrees. The court does not care what the schedule is as long as both parties agree.