Magic, The "should I or should I not go" questions are the same for any function, i.e., be it work or personal. The bottom line is this...only you know whether you can attend, keep your mouth shut and keep the expectations at zero.
Sit down in a quiet place and ask yourself...are you strong enough to do this? Can you go and not have expectations? Can you go and not have conversations about the relationship? If your answer is no...then you have your answer...but you have to be honest w/yourself.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.