I used to be bothered by ambiguous endings in novels and stories, up until I started writing them. Now it would be hypocritical for me to be too disappointed about it. Anytime a writer decides to end a story with questions, typically, the author feels that the answers to these questions are unimportant. In this case, whether J. dies or goes on to break the record, is immaterial. Whitehead wants us to focus on what happened during the story, rather than what Pamela and J. decided to name their babies, assuming J. didn't die. If either conclusion was given, it would alter the focus in (presumably) a way that Whitehead didn't want to alter it.
As far as giving a newpaper article on the shooting, to wrap the story up, it would have been interesting to include one, but avoid giving any facts beyond what we already know at that point. "Two unidentified men were shot, sources indicate they were journalists visiting Talcott for the John Henry Days Celebration." They could even go further and drop subtle, conflicting hints, suggesting each of the journalists. Then again, this would draw more attention to the unanswered, leaving less focus on the parts of the story that are told.