The story: wealthy Manhattanites pay disabled kids to pose as family members to get preferred positions in line.
Euvoluntary or not? The rich New Yorkers (and what better way to rile up anti-elite sentiments than to mutter "Upper East Side"?) are better off (presumably their time is valuable even when on vacation?), the disabled faux children are better off (making over a grand a day slumming it at Disneyworld? Sign me up) and the park itself is no worse off, assuming that the marginal patron isn't so offended as to stay home. And what of that marginal patron? They have to wait a little bit longer, all those little bits add up, and this whole thing probably ends up a wash overall, just a transfer like in any other market.
Queue position is a scarce good, but it's one imposed by the organization of the park. Is it fair to say that it's natural in the same sense the relative scarcity of diamonds or baleen whales is natural or is it artificial the same way immigration visas are artificial? A person (more likely a planning committee) made the decision about how many passengers a particular ride would be able to accommodate over the life of the ride and designed accordingly. In this sense, the queue is artificial, but they also designed it with profit maximization in mind, which means they were doing their best to match customer satisfaction with the fixed costs of ride design and construction. I doubt that this queue-hopping was anywhere in the original plans.
So which is it? Natural or artificial? And however you answer the question, does this practice offend your sense of justice? Of fairness? Of euvoluntarity?