I have to agree with the rest of everyone and say that I'm scratching my head a bit with this one. Granted, we don't have the whole story and know whether or not there was long discussion after they finished up or not. However, I know that I would have issues with the misses if she wouldn't go down on me and then said sure to a play partner.
As for the peer pressure, I can see that one because I kind of felt similar in the beginning.
On the lighter side......
....after they guys finished going down on the girls, did they come up and have the "Tastes Great, Less Filling" debate???