I would suggest waiting. Don't respond, and don't call him. Let him call you to extend the invite. A text invite is not good enough for the likes of lwb.
When he calls, tell him you were planning on doing something else. Like washing your hair or something. OK, don't say that, but you should make him squirm. Tell him you need to think about it and ask him to call back in an hour. Make him pursue you.
Then, think about whether you want to go. What do you want to do? What does this mean to you?
