I'm thinking of turning down my son and his wife's dinner invite because they live in a small apartment.
What don't you like about their apartment?
My son and his wife have a chicken farm at their apartment
It is understandable that you don't want to go to a place that has a chicken farm. It can smell bad and make your experience suck.
But I just have to deal with it. I just feel that if I go, then my SIL will be rude to me and I will be miserable.
Just make plans for them a different time. It's okay to turn down the invite if you really don't want to go.