Just enjoy the rest of the company. I'm assuming there will be more than just the 4 of you? People tend to converse with the people the know and get along with in social situations and just not interact with those they don't know or don't care for. That's just part of socializing in larger groups. Don't make the party about disliking these two people. Make it about the other people and the friend you are honoring. Avoiding entire social situations because one or two people bother you tends to just keep you isolated.