I am going to walk through this discomfort though. I have to.
There's your answer. Similar sitch here, except my wife's affair lasted quite a few months. But it seemed to be at its peak around the time of our beach vacation in 2012, and her behavior during the vacation was really bad. Although OM was over a thousand miles away, she might as well have brought him with us. He was certainly there in spirit.
So we went again this year after taking last year off. I triggered badly for a week before we left. WW looked for a hole to crawl into every time I walked into the room, it was that uncomfortable.
But then the time came to leave, and we ended up having an all-time great family vacation. I got through it simply by enjoying it and taking pleasure in my family's happiness. Also, by visiting with family and old friends, playing golf, drinking, getting a good tan, eating great seafood, swimming, and having some romantic alone time with my wife.
No magical formula, but there's something to be said for confronting something head-on. For not letting the actions of others define you or defeat you, or change you for the worse. Often the fear doesn't live up to the (internal) hype, anyway.