Oh dear, I see the MOTHERS MUST BE SILENT MARTYRS drums are beating again.
Of course it is NOT in any way unreasonable for you to feel this and want not to have your face rubbed in it.
You are a normal human being, with feelings which will don't magically vanish because you're a mother. If a man treats a woman like shit, she's supposed to don a pair of angelic wings and a halo and is not even even allowed to say :"I don't want to see him ever again" without the screaming hysterics starting in on them.
So yep, it's normal to want to avoid him, and absolutely normal to want nothing to do with his wife. I am so sorry his treatment of you made you feel so low.
However, you can't keep him away from events and shouldn't try. He is probably enjoying how much misery he is causing you so do try not to show that you care if he turns up with his wife. If forced to interact at all, just a polite nod and calm very basic communication.
He does have a right to go if he wants to and if he cares at all about his child HE will make the effort to find out what's happening and do so.
But of COURSE it's not your job to keep him in any kind of loop re events. He should be checking in with the school/clubs etc himself, you're not his secretary or his partner anymore.
Stop communicating with him at all except when it comes to organising drop off or pick up of your child or any other very basic things you must communicate with him for.
See if you can get a friend to go with for support in case he turns up with the wife, it's amazing how much better it feels with another human by your side who can give you a smile or a word of comfort.
And maybe consider some grief and loss counselling. Your feelings are completely normal and very standard - you are grieving what should have or could have been, the loss of the happy future you imagined for you and your son. Grief counselling is not just about death, you can get grief and loss counselling for divorces and etc too.
Good luck.