Why they flew away

Adaptations of Peter Pan frequently invent reasons why Wendy feels she must fly away to Neverland with Peter and not grow up. In the 1953 Disney film, she is about to be moved out of the nursery because she has become too old to share the nursery with her brothers. The 2003 film created the odious character of Aunt Millicent (though played by a lovely actress, Lynn Redgrave), who disapproves of the children's tales of adventures and wants Wendy to be a proper society lady. Wendy also begins drawing pictures of a mysterious boy paying visits to her in her bed, to the consternation of all the adults in her life.

Flora White, 1914

But when I was young, I wouldn't have needed much convincing to fly away to a beautiful place of freedom and adventure, and I don't believe most children would. These filmmakers (and many writers) must find that reality distasteful, given the lengths they go to showing that the Darling children need more impetus to fly away with Peter than simple desire.This change undercuts the point of J.M. Barrie's book. To Barrie, that desire was not only sufficient, but part of the inherent nature of children.

For instance, Barrie describes how Peter Pan convinces Wendy and Michael and John to join him by telling them exciting tales of mermaids and pirates, and how he appeals to Wendy's desire to take care of boys who have never had anyone to nurture them. Peter's childishness is not sugarcoated either, and in fact is integral to the story. For example, on their way through the skies to Neverland:

He could go so much faster than they that he would suddenly shoot out of sight, to have some adventure in which they had no share. He would come down laughing over something fearfully funny he had been saying to a star, but he had already forgotten what it was, or he would come up with mermaid scales still sticking to him, and yet not be able to say for certain what had been happening. It was really rather irritating to children who had never seen a mermaid.

"And if he forgets them so quickly," Wendy argued, "how can we expect that he will go on remembering us?"

Mabel Lucie Attwell, 1921

But even Wendy's memory of her loved ones is not consistent, despite the fact that "in the end she grew up of her own free will a day quicker than other girls"--in contrast to the depiction of Wendy as a girl who didn't want to grow up.

As time wore on did she think much about the beloved parents she had left behind her? This is a difficult question, because it is quite impossible to say how time does wear on in the Neverland, where it is calculated by moons and suns, and there are ever so many more of them than on the mainland. But I am afraid that Wendy did not really worry about her father and mother; she was absolutely confident that they would always keep the window open for her to fly back by, and this gave her complete ease of mind. What did disturb her at times was that John remembered his parents vaguely only, as people he had once known, while Michael was quite willing to believe that she was really his mother. 

Anne Graham Johnstone, 1988

Perhaps Barrie's easy acceptance of that quality of children is part of what makes Peter Pan not solely a children's book. As he himself ends his tale, 

...and thus it will go on, so long as children are gay and innocent and heartless.

Heartless. Barrie was able to like and appreciate children despite this capacity. It's unfortunate so many others who revisit the story of Peter Pan don't feel the same, or trust that their audiences might.