Parents who pay child support are often concerned that the money are actually used for the needs of the children, rather than their ex-spouse.
Child support is designed to cover the necessities, such as food, clothing, shelter, basic medical care, etc. In addition to a base amount of support, the parents may also be expected to pay additional amounts for extraordinary medical care, private schools, sports and other activities, and so on. In some states, the parents can be ordered to pay for all or part of college costs, as well.
So what if the receiving parent spends the money on themselves, rather than the children?
Usually, it does not matter. As long as the children are not being neglected, the receiving parent does not have to account for how they spend the money. Some costs, such as the rent or mortgage, utilities, groceries, etc. are partially for the children and partially for the parent. It wouldn't be reasonable to ask a parent to account for every dime when so many of these "mixed costs" are involved.
Sometimes, the paying parent decides to give the money directly to their children, especially if the children are teenagers and need money for gas and entertainment. Their reasoning is that at least they know the kids are getting the money.
While you are free to give your children whatever you like, realize that paying them directly does not reduce your obligation to pay your ex-spouse. Remember, he or she is paying the rent and buying the groceries.
The best course of action is to pay your spouse the amount you owe, and think of that money as being used for the children's expenses and for basic household expenses. Assume any "pampering" or luxuries your ex-spouse is getting are being paid for from their own money. Whether or not this is true, believing it will benefit your attitude and mental state immensely.