I understand what the OP is trying to convey. Yes, of course we all spend money on our kids’ soccer, music, medical, etc. But her point is that the form says that they have THREE kids in the household, not SIX. So whatever the calculations are for the expense of having a child, on their FA form the calculation will consider three children—even though their financial situation closely mimics a household of six children. Surely, if there were six kids in a household with, say, an income of $100k, that would produce a different FA result from that of a household of the same income with three kids.
Maybe the solution is to increase the “official” amount of your husband’s child-support payments to reflect what he actually is giving them.