At the end of the day, it should be the child’s choice (unless a Rav explicitly prohibits one way or the other).
A Halachic authority should of course be consulted in all cases…80
There is a minhag not to attend the chuppah, but as far as I know, that does not mean that a child who wants to attend should be stopped from doing so. I know of plenty of people who have attended a parent’s chuppah and plenty who have not.
A Halachic authority should of course be consulted in all cases…80
I didn’t attend my mother’s chuppah because it was too painful for me and I was very thankful to have the minhag to rely on; when my father remarried years later, although I would have been ok with attending the chuppah (I was older, more mature, and happy that both my parents were happy), I once again relied on the minhag so as not to cause pain to my mother by doing for my father what I couldn’t bring myself to do for her.
Every situation is different; also, be aware that unless the children are adults, it is VERY unlikely that they will be happy for the marrying parent. Divorce or death usually doesn’t make much of a difference in that respect. The day of remarriage is like the day of the divorce/death all over again, and is EXTRAORDINARILY painful for the child. While the child must respect the parent, their decision, and their spouse, they CANNOT be forced to feel good or happy about the situation.