"Should I continue to put myself in a position where I would be exposed to that?"
Yes. Remember that what they are trying to do is bother you, to make you feel shame. If you decide not to attend a function because they -- your Witness family -- will be there, then they have succeeded. Remember that is it THEY who are wrong -- not you. The shunning might hurt, but stand up for yourself and what you believe. If you give in, then you will just bolster their belief that they are right and you are wrong.
Were I you, I would attend the event and treat them just as you might treat anyone else. Now, I don't know if they are pleased to be doing what they're doing, or if they only do it because they are supposed to; but you are under NO obligation to avoid them or treat THEM badly. Just briefly say hello to them, and say that you hope they are doing well (and, oh, how little Johnny's grown). DON'T say or ask anything, of course, that would require them to make any sort of response at all. Take control of the situation; otherwise, THEY will.
By doing this, you might been asked by someone else to tone it down because you're making your Witness family members uncomfortable. Reply that you are simply being friendly, because despite how they treat you, you are still their sibling, and you will treat them as such. There is, after all, no reason for you to shun them. Be nice. They're your family. I wouldn't spend a lot of time with them at all, but I see no reason why you shouldn't say your hello's and whatnot. Watch 'em squirm.
So in short, stand your ground and be a part of your family. Don't turn and run away with your tail between your legs. If you look happy and pleased with your decision, they will notice. They will notice that, hey, you don't look so unhappy after all -- even when being shunned.