Who is Walter, Irene, William, Carol from The Vintage Book of Contemporary American Short Stories and what is their importance?

Walter is the protagonist of All the Way in Flagstaff, Arizona, though he is imperfect and an alcoholic. The reader sees him spending time with his family, on a picnic where they argue and play and do a lot of normal family things. However, the narration confirms strain between him and his wife and eventually, she leaves him, which deeply hurts and changes him as a man.