REally LTS on the sofa...
You pretty much covered the tabus there... most of them have been done to death in recent years although there are still places that sing them... I don't think they've all quite reached Pitcairn Island yet.... :D
The best thing is to just play by ear, as you would in trying not to sing a 'regular's' song...discrete questioning of the host before the evening starts helps, or just attending for a few weeks before you perform, to get the lay of the land as it were.
You could try jiggling the arrangement/tune so the average punter doesn't quite recognise it - in the way of lift muzak where you know the tune but can't quite place it.... but better - that often works.
Good luck with it!
Oh, and avoid 'The Green fields of France (Willy McBride) unless it is actually Remembrance Sunday or Armistice Day.