Aw Emerald I really feel for you. In the next few days cuddle up to your husband and let it just be the two of you, enjoying each others company. Have a good cry if you want to, let it out. It wasn't how it was supposed to be, was it? I know, I got uninvited to my ED's wedding last year, I never imagined that happening neither and it really upset me. You need to recover from this though because you were wound up about it for some time beforehand and it will have taken it out of you. Good food, some good films, good cuddles and sleep and you will feel better, hopefully, very soon.
You did go, no one can take that away from you or accuse you of not bothering. In time your son might realise that his mother will always be there for him but at the moment he is all loved up and he will probably not know if he has been coming or going. Plus, he probably didn't do the table plan. Give it a week or two, recover and then maybe drop them a line saying thank you for the invite and you hope that they had a lovely day. Then leave it and take it from there, see what happens. But if nothing does, move on, enjoy your new little grandchild and your daughters and your husband. And, if it were me, I would pity your mother, if she has to make such a show of herself. People should know that she is the children's great gran, she shouldn't have to shout it from the rooftops and make a spectacle. Kids grow, they will decide to come and see you if they want to when they are older. It'd be on their terms then, not their parents. You take care love, Xxx