am I doing the right thing?
I will try and be quick about the situation, since I know we all don't have all day. 
I married my husband five years ago and he has 4 children that are all adults they were 19-24. None of them really get along with their mother calling her by her first name or not even talking to her at all. They have been disrespectful to me on numerous occasions that I finally just stopped doing things with them, and it caused a wedge between me and spouse for a time. Well, we did separate for a year and half, but it was a lot of other stuff too, but after time and counseling we decided to try to reconcile. Now, of course they are being extremely hateful and rude to their dad about it. They are calling him and I both obscene names, and saying that I am this and that...meanwhile I have yet to even be in the same with any of them. The thing is his son, which is the only child I had somewhat gotten along with is getting married and asked me to attend his wedding. I would like to go and be there to show I am not "scared" of these girls, but then I wonder if I am just setting myself up for an even that I should just bow out of. They believe they can control all situations and their father...it is sad, and I have realized a lot of their problems are not me per se but with their parents.
Thanks for reading!!
Good advice steperg.
Good advice steperg. Shortly after I moved in with DH and 27 year-old SD, we started having problems. When ever she approached him about me, he stood up for me. At this point, things are much better because I refused to live in a battlezone and life is much too short for the BS.
Why is your DH allowing his adult children to disrespect both of you with the name calling? It's pathetic. He needs to have a meeting with them and demand that they respect both of you, and until that happens he will have nothing else do to with them .. . period. They're only doing it because they know they can get away with it.
If I were you, I'd decline going to the wedding. The last thing you need is more drama, and for some people all it takes if a few drinks to loosen lips. I wouldn't want to put myself in that situation. But if DH speaks to them in advance and they agree to act in a civil and respectful manner toward you both, then and only then would I reconsider. Either way, good luck.
Explain to ss you would love
Explain to ss you would love to attend, but due to conflicts with siblings (which i'm sure he's aware of), you will have to decline in fear of an altercation ruining his day.
i also agree getting dh to speak with the rest of the other ungreatful, self entitled shits and get a promise they will be civil at ss wedding.... but talk is cheap and there is no guarantee they will fulfill any of the lies they blow up dh's ass....
for the rest --- WTF? adults and treat you both like crap?? first of all, even as a woman, it appears my balls are bigger than dh's...... so maybe purchase him a set..... and the two of you should write them off until they grow out of their issues.... disrespect bm, too? well now, maybe this all goes back to dh and that's why his balls are lost when correcting his followers... somewhere they learned this behavior..... in the end they are adults, so as much as i would want to take the high road -- i would boot them w/dh's support or hit the road myself...
good luck........