I'm not going to make it to my boyfriend's surgery
What would cause you to miss your boyfriend's surgery?
I'm not going to attend his surgery because its scheduled on a Friday. It's my friday night.
You should sacrifice one party night for your boyfriend.  In times of need, your family needs you more than your drinking friends.
Friday or not, I'm still not going.
This is something that is beyond your night.  Supporting someone in a long tern relationship will be more beneficial in the long run.