Something that has helped me in the past with going to family functions... is to think up some planned responses... when people say things like... Your dad was such a great man... Or you must really miss your father... I would pick one thing that was not upsetting to me or neutral to me like in response to the "great man" thing... I would say...it was wonderful that he serviced his country in WWII... etc.....

Just planned things so I didn't feel like I was lying and also so I didn't blurt out what I was really thinking.