Should I witness my friends marriage?

My husband and I are best friends with an awesome guy. I love him to death as a brother. Well, he has been miserably single for the last five months. His fiance (who has a two and half year old little boy) broke up with him and refused him contact with her son (Not his) who calls him dad.That was a sad story. Well, about two weeks ago she called his sister up, wanted to bring the son over for a visit but didn't want my friend (further referred to as Mike) to be there. Well my friends sister said that she would not tell Mike to leave. The ex (further refered to as Ashley) still came over and ended up getting back together. Well now all is good for about a week until Mike announces to my husband and I that he and Ashley are getting married December 10th. He then goes to Kay's buys her a half carat diamond ring. They go to a theme park with us for a day and during that day they are either furious with each other or all over each other. To the point that it makes me and my husband uncomfortable. She paid for nothing and demanded allot of things. She got mad at him for having a beer, etc. etc. etc. I also saw a side of my friend that I had never seen before. He got offened at the least little thing. Then, after we got back, he dropped another bomb on us. They were getting married in two weeks at the courthouse and they need us to witness. Now her family strongly disapproves and his has tried to talk him out of it but with no sucess. His family is so involved that I wonder why they wouldnt be the witness. So, with this so messed up I must wonder if me and my husband should support my friend because this is his decision to make, or if we shouldn't.Let me add they have dated for 2 and 1/2 years on and off breaking up for 5 times.