Advise for Attending a Swinger's Party?

Me and my husband have beeh invited to attend a swingers party. We have been invited before but have never atended. It's nt that we havn't wanted to just that my nevers get the better of me the closer we get to the date of the party. I guess I'm nerves because I feel a little pressured to deffinently swing at this party.I mean what if I don't like the couple that'shitting on us? How do you turn them down nicely with out hurting their feelings? What if they don't like us? Whatif thy don't like me. I'm a BBW what if that's no ones type? I guess I'm nerves about getting let down and letting everyone else down. I just wish I could get over my insecuritys. We've had 3 somes with other girls befor but never with another guy and they've gone fine and I have no problem hitting on weman when I'm drinking. Is there any advise you can give me that might be able to help me?