Mark, you can certainly look at the entire family as a collective Protagonist because at the end of the day, this is a story about a dysfunctional group becoming — at least temporarily — a bit more functional (the beeping car horn at the end of the film as the VW bus drives away suggests their problems are not going away without further struggle).
I just find it interesting to explore the individual tracks each character goes on. On two extremes, we have Grandpa and Frank. The former is cocksure of his opinions, even if he is a heroin addict. Frank is the most deconstructed figure at the beginning of the story, a suicide survivor. It’s an interesting pairing of these two considering their respective proximity to death.
Then you have the parents: Sheryl and Richard. The former is pretty much a rock for the family, the closest character to existing in an ‘authentic’ state. She supports others and conveys little in the way of whatever inner conflicts she may have. In contrast to Richard who is living a completely inauthentic life, looking at his book as a form of external validation, a way to avoid dealing with his own insecurities and flaws. In the end, his embrace of Olive’s ‘failure’ on stage is a clear sign of his own character transformation in contrast to his whole “you’ve got to be in it to win it” attitude at the beginning of the story.
The next pairing: The Siblings, Olive and Dwayne. Dwayne despises his family so much so, he wants to be an airplane pilot, quite literally fly 35,000 feet above these people he’s been forced to live with and perceives as being failures. Olive doesn’t have that negative energy toward her family, yet she, too, wants to ‘fly away’ from her reality by becoming a beauty queen. If we were to add about 8 years to Olive’s character, I figure there’s a good chance she would be as cynical as her step-brother is now. And yet, they have a special bond witness that lovely moment where she walks down the hillside and rests her head on Dwayne’s shoulder after his “fuuuuuccckkk” meltdown.
And so, six characters a collective family, and yet their own individual journeys (I would argue Richard, Frank, and Dwayne are most tethered to the story’s central theme: What is success? What is failure?) as well as some interesting couplings as well.