My experience as a disfellowshipped person for the past 20 years is that the JW parents will have hell to pay if the elders find out that they went to their df'd child's wedding for two reasons:1. the child is disfellowshipped and 2. the wedding is worldly. I've heard that in my old congregation a woman was advised against attending her son's wedding by the elders. He was never baptized and therefore not disfellowshipped. He also arranged it so his wedding wouldn't be held in a church or the ceremony performed by a minister. That still wasn't good enough. She was not to attend, because it was a worldly function.
My mother and all of our JW relatives did not attend a family reunion last fall, because I and some of my disfellowshipped cousins were there. It was a sure thing that none of the JW's in our family would be there, because my mother turned her JW sister in for having her disfellowshipped kids to the wake held at her house for a fleshly brother (who wasn't a JW). She got in BIG TROUBLE for that. If death doesn't transcend the bounds of the WTB&T's rigid rules, I don't see where a wedding would. It's a real shame, but that's how it is when your relatives remain Watchtower slaves.