what's right for your child? The child still needs to be cared for, are you willing to take up the slack that the reduction in child support will make, in exchange for not fighting with him? Whatever you decide, it still needs to get addressed by the court. If the state is collecting child support from him and dispersing it to you, there may not be a choice in the matter. If he pays you directly, you can agree to a new amount outside the guidelines, but then again, a judge may not accept it. I know with my state, child support can be set by DHS, using the state guidelines and without a specific court order setting the amount. Or, the court can set the amount, again using the state guidelines, and DHS can be used only as a collection agency (where they have no jurisdiction over the amount set...they have to follow the court order).
Ultimately, it boils down to what is best for your child.