McGuane talks, in the New Yorker, about his writing of the story:
I often write until a story strikes some impasse, which can be terminal. That was nearly the case with “Balloons.” But I was helped by a dream in which the married woman, Joan, was dead. It changed everything and greatly enlarged the prospects for making a story out of something that had baffled me, without causing me to lose interest in it.
This statement suggests that McGuane follows a story where it leads him, rather than setting out on the undertaking with a clear end in sight.
In the article he goes on to say, when asked about the fact that a number of his recent stories have explored the ups and downs of marriages and relationships in small towns in Montana and whether he is writing a series:
I hope not. Thinking about marriages has a retrograde quality, since it’s been a long time since it made sense to get married at all. I belong to this fading cohort, so I go on wondering about such hopeful arrangements. In fact, any outcome of hope interests me, in marriage or otherwise.
From these responses my own interpretation would be that McGuane writes about what interests him, but not with a strong view at the outset of what the finished story will be. This makes it unlikely that he is setting out with the idea of having a deeper message to ‘convey’.
The narrator makes an apparently scathing reference to Benjamin Franklin’s ‘obscure dictum’ on the use of venery ( the pursuit of sexual gratification), the full Franklin line being:
Rarely use venery but for health or offspring, never to dullness, weakness, or the injury of your own or another’s peace’
Although the narrator makes that reference early in his relationship with Joan, the dictum seems, in the end, to have been good advice.
It is possible to read this as part of a larger theme of hope, we hope we will be happy, we hope our partners will be loyal, that our good fortune will be ‘tightly held’, that we can be wiser than Old Ben Franklin.
But this is my personal thinking on the story, if you want the view of the literary world at large, you may need to wait more than a week from publication.