Could you talk to mom with the idea that you know dad's dont' always read labels or notice details like how long the pants are and would it be possible to get some more size appropriate clothes for their bin so that they have something to wear and suggest when you send the too big clothes home that they put them aside so they don't get chosen again till they will actually fit - kind of like telling them what to do cause it sounds like it hasn't occurred to them to sort by size.