I seriously wouldnt give them the time of day. Exit the way you want and have nothing to do with them, regardless of what your family want you to do. You need to live your life as you see fit away from there judging eyes... I seriously wouldnt give them the benefit of turning up for the JC.
Can you explain why you feel the need to attend this JC? Expecially when it means they will just degrade you! Nobody has the right to do this to you so Im at a loss as to why you would want to put yourself through this, that is unless you feel some mad need to be humiliated by them.
You can either attend, then get reproved and then live the rest of your life beneath the radar or decide here and now that they really arent the 'truth' and that you dont want anything more to do with them... The choice is yours. Without understanding your reasons for wanting to attend I dont think we can offer you much more advice.... xx