How did the parent-child relationship shape identities and determine individual paths to adulthood?
I think the primary focus here would be Ray and his father. The love of baseball passed on from the father to the son, embodied by the former and instilled in the latter. Ray's path as an adult is influenced by the love of baseball and in what his father imparted within him. The dreams of Johnny playing the game he loves is represented by Ray's dream of building and sustaining the baseball field. While it is not openly suggested in the novel, Ray's actions are heavily influenced by those of his father.
Additionally, it can be suggested that Ray is trying to extend where his father did not succeed. Whereas his father had to give up the game he loved when he married and assumed the role of family caretaker, Ray is trying to extend that dream in keeping the field and ensuring its vitality. Ray's life and the steps taken to forge his identity as an adult stem back to his childhood and the relationship he shared with his father.