My brother was Df'd for the second time when my father died. Our immediate family never shunned my brother (my fathers side of the family did).
The brother that handled the talk was very very good. He asked us to tell him some personal things about our father so he could include them in the talk. My brother wrote an excellet letter about how loving he was, how no matter what he did he never turned his back on him, how unconditional his love was etc. The brother giving the talk actually read the whole letter during the service.
Almost everyone at the hall was very welcoming to my brother. One sister (who was very well known) made it a point to stand beside my brother, almost like saying if I can talk and associate with him so can you! Sadly she has passed on - gawd I miss her!
The only one to really give us a problem was my uncle, my fathers super duper elder brother. He would barely look at my brother, and the only thing he said to him was "you know what you have to do". Nothing about our father (his brother) passing etc. What a prick!!!
We had a lunch at the hall, and my brother stayed and ate. We had some relatives and close friends back to the house afterwards, and ate supper and my brother was there.
I think it depends on 1) how your parents treated you - were they militant in their shunning? and 2) what are the people like at the hall?
You have every right to be there if that's where you want to be! Go and hold your head high! If you really don't want to go - don't and I think Blondie had an excellent suggestion. Hold a service that would mean something to you.
BB