Not necessarily, as you can see. You're right, once our kids are officially grown, they can worry us even more. I wouldn't be surprised if one of my sons didn't just call me one day and say, "I'm married!" However, they both affirm that they plan to finish college first.
Yes, your son sounds like he has made a poor choice, but it is his life and he will lie on the bed he has made. Oh, dear, I'm sounding like my own mother!
I was 32 when I told my parents I was getting married. They were not happy with my choice. (My T told me they wouldn't be happy with anyone. Truth is, they didn't ever want me to marry. I was supposed to be the daughter who stayed single and looked after them.) But I have been married to the same guy for 24 years and we have two wonderful children. No, he's not perfect. But I'm lucky, to be honest, that HE has stayed with me.
Let's hope your perception is wrong. But for his sake, I think it would be nice to show up at the wedding with a smile. And if you do cry, remember that it's expected of the mothers!