My suggestion would be to put out of your mind any speculation you have as to his motivations for inviting you. You'll never know. He might not know himself. And ignore anything you might have told yourself about what will happen while you're there. The wives might not ask you anything at all. In that situation, I wouldn't dream of asking. There's a lot of mind-reading and future-predicting going on in those posts. It is a kind of control - wanting to choose what you do in order to get the best possible reaction from your H.
Instead, have a think about yourself and your daughter. Do you want to go? Would it be fun, just on its own terms? If not fun, would it be of benefit to your daughter to have you there? Those seem like the only factors to take into account when you make your decision.
