Listen what ever it costs you that is reasonable has to be better than him paying an unbalanced amount for the next 11 years until they are 18 at least.  The court would not terminate the child support because he is still obligated to pay some portion we just have to figure out how much based upon Arkansas child support guidelines.  But he can indeed bring a motion to modify the child support and to reduce it again base upon the child support guidelines.  And now that she has a job too that income will be calculated in.  You should get some legal help here to do this correctly.  Good luck.