@Bonjourfreddie rubicon legally then (because that's what I am saying) how does the parents status change having witnessed (not legally just with their eyes) their childs wedding? enlighten me.
Not that I believe that should be the criterion for whether or not people feel they would like to attend, but as it happens, the parents ARE directly affected legally by their children getting married, as they are no longer the next of kin or the beneficiaries if they die intestate.
But if you think that that should be the basis on which people should or shouldn't want to attend an event, absolutely none of it matters and no one should ever attend anything - weddings, barmitzvahs, funerals, etc. unless it has a direct impact on their own legal status.
Oh and by the way, the distinction between 'legally witnessing' and 'seeing with your own eyes' is not the huge gulf you seem to think it is. Our mothers were our two witnesses, so they are legally recorded in the register as having been there (our fathers are named on the marriage certificate anyway as per the current, sexist UK law).
Above all, the point is that the parents WERE very unhappy and upset by this, and that the OP and her husband deliberately lied to them knowing that they would be. And she's trying to blame someone else for it. That's shit and it's not OK no matter how much you try to twist it.