I'm thinking of not asking my boyfriend first to the dance
How will your boyfriend react when you don't ask him first?
I don't think he will be the happy about it.
It's okay to have friends and other people to hang out with, but it's a dance which implies intimacy, which can let your boyfriend feel a little betrayed. How about just going with him, and hanging out with those other people in a less intimate event?
What I do isn't cheating, but I'm going to make him feel it anyway.
It does look like cheating. Your partner should be your first preference as a dancing partner. You should ask him first.