A few phrases stand out from your posts.
About you and your family, and your view of the wedding:
it all felt full of weak reasons really [his explanation]
I have never been one to conceal my feelings
I don't think it's realistic of me to just react with platitudes
No one in this house holds back really...
About his wife:
she is sometimes difficult to read though, she's polite but doesn't really share a lot.
I was all ready to make her part of our family but she seems to like to keep us at arms length.
Your son has obviously chosen someone with a quite different approach to emotions than the one he was brought up with. This naturally means there are going to be differences in the way their relationships work - both their relationship with one another and their joint one with you as a family - compared to how you do things. Maybe the fact that your son has chosen someone so different suggests that maybe he’s not as comfortable with the “nobody holds back” approach as you are? We all have emotions and reactions to certain situations and behaviour, but not every thought that goes through our minds has to come out of our mouths.
It sounds to me like your son and his wife knew that, if they’d told you about any of this beforehand, everyone - you, your husband, your other children - would have had an opinion, and not been shy expressing it. Sometimes the best way to make sure a decision is yours and yours alone is to keep it private until it’s made.
I do understand why you’re upset and disappointed. Of course it’s not unnatural to want to be part of your child’s wedding day. But you have two choices now. You can either accept that it’s happened and be part of the rest of his life, or you can have the big drama where everyone chimes in - which might just be the confirmation they need that they did exactly the right thing.