Would you be made if your boyfriend asked you to attend a friends wedding, you tell him you can’t because your son had surgery the day?
No because I would have said "go without me". You're not even married to him and it doesn't sound like this is even his son. There's no reason he should blow of HIS friend's wedding just because you can't go. If you're angry you're being ridiculous.
Him staying away from a family event helps you or your son, how exactly? Jealous, much? You're not attached at the hip. He can go to things and it won't diminish you one bit. If you didn't have a boyfriend, is everybody supposed to stay home and do nothing, because you need to take care of your son for the day?
I'd say it depends on whose wedding it is (close brother vs. distant cousin or an old high school friend he's barely in touch with) along with how long you two have been together and how serious your relationship has been going on.
The Lord Humungus.
He had an obligation t attend the wedding, you couldn't go. You have no right to be mad at him.
Mad? No. Expecting him to drop his obligations to accommodate yours, is ideal. But not reality. If you want him to stay, tell him. Otherwise, it's normal for his dense a$s to go on without you.