Child support is not necessarily for the benefit of the receiving parent, it is for the benefit and the entitlement of the children themselves. With that said, Courts will generally not allow child support to be waived. The times they will are if the obligor pays directly for the children's expense such as private school, etc.. The child support amount doesn't necessarily have to reflect the amount listed on the child support guideline list in the texas family code, (for 4 kids it is 35%-40%). You guys can agree to the minimal guidelines and explain to the court why.
Largely, it depends on the court and their willingness to allow for the waiver. Here in Houston, the family court almost always never signs the order allowing for waiver of child support. I know it doesn't relate to you since your in the Dallas area courts. Sorry.
Consult a local attorney to assist you guys, or consult a local legal clinics sponsored by the local law schools (SMU, Texas wesleyan law school) or your local bar associations where great attorneys volunteer their time and service for free or reduced price for advice and/or representation.
Hope this helps and good luck
Different judges have different policies on this question. Some judges will routinely waive child support if agreed to the parties, especially if the parties are splitting possession 50/50 and both parents are employed and can support the children without any support. Some judges do not like to waive child support. You should contact a local attorney that is familiar with the judge of the court where your case is filed.