Alma was saying something about taking his friend to the Knife & Fork for supper instead of cooking it was so hot, if they could get a baby-sitter, but Ennis said more likely he'd just go out with Jack and get drunk. Jack was not a restaurant type, he said, thinking of the dirty spoons sticking out of the cans of cold beans balanced on the log.
Mikaela, you right; Ennis was attempting to make up excuses why he did not want Alma to be with him and Jack. And, while it does not seem that way so much in the movie, Alma was a person who was miserable and a whiner. He should have never married her in the first place.
I have a friend who is now separated from his wife; but, I certainly did not want to go anywhere with him when she was along, especially if we went to some kind of superstore. That's because she would strongly hint that I buy something for her or her daughters in the store. I say "her daughters" because I actually know that his mother and his sister both have said the could not be a biological father and his father did not believe that the girls were his biological grandaughters. I definitely agree with his father and, in a way, my friend seems to agree, too. But, both he and his father accept them as family. Oh, they accepted me, too.