Calculation of child support with divorce mediation in MA

Thanks for your question. The mediator does not "decide" about child support or any other issues.  You may be confusing arbitration with mediation.  Mediation is a non-binding, collaborative effort in which the mediator simply attempts to help the two parties reach agreements on a variety of issues.  If there is no agreement then, at least with respect to the disputed issue, the mediator has no power to enforce a solution. 

The special circumstances you mention will likely need to be discussed in the mediation. Similarly, in attempting to reach an accord, the mediator will likely encourage you and your wife to think about and discuss other child-related expenses that may have a direct bearing on the question of the appropriate amount of child support.  These other expenses may include such things as summer camps, tutoring, music or dance lessons, sports related expenses, etc.

With respect to deviation from the MA child support guidelines, the parties to a mediation can agree to deviate, but the court will still have the final say on whether the deviation is warranted.  To gain court approval, the parties will need to convince the court that: (1) the amount called for by the guidelines would be unjust or inappropriate given the unique circumstances of the case; (2) there are specific facts that justify the departure from the guidelines; and (the all important question in all issues related to children in a divorce) (3) departure from the guidelines would be in the best interests of the child. I encourage you to talk to a MA divorce mediator.  Most offer free consultations in which they can answer any other questions you have about the process.  Good luck.