Your children’s mother can use the child support you pay her for anything she likes. Her expenditure of these funds does not have to be even remotely related to the children’s reasonable/legitimate needs. If she wants to take the money and gamble it away in Las Vegas (or some other place), she can do it. What a great child support system we have here in NC!
You can’t “require” your ex-wife to do anything with the child support money you pay her. Only the court can do that. If you believe ex-wife is misusing the child support money and you can’t reason with her, you need to go back to court and try to convince a judge to put a stop to it.
On a related note, does your ex-wife not provide any financial support to you children? If she is able to provide support, according to state law and court decisions she must provide support. The fact that a parent happens to be the custodial parent does not relieve that parent of the obligation to provide financial support based on his/her ability to do so.