We'll just have to agree to disagree Bibbity and*Hithere*. While I acknowledge a divorced wife or husband's understandable desire for a clean break, that isn't possible when there are children involved is it.
Contact has to be maintained by the parents because they had children together. As for an ex i.l.; the 'phone rings, you answer, it's ex m.i.l. 'hello it's ....... can I speak too ......' answer 'yes I'll get .......' or 'sorry not at the moment, can you call (give another day, time or both'. It's not difficult is it and even if you could never stand your in law's and are glad to be free of them, do it for the sake of your children.