This being the A, or This being that y'all are having trouble?
I would say that close friends and family know that you are having trouble already but it wouldn't hurt anything to acknowledge it. This may let them know you're willing to discuss it.
I would not bring up the affair. The reason I say this is because this is still very new to you and you don't know where things will end up. If she starts telling people that's one thing, but if you do it can be misinterpreted as trying to lash out. Also if everything starts working out, the fact that less people know may be one less outside pressure to overcome.
But, that's just my opinion. I'm sure others view it differently.
