Themes in Peter Pan

Hey guys! it's my first time posting in this forum and i was wondering if you guys could help me out.
I have to write a 4000 word essay and the topic i chose was focusing on the theme of growing up in J.M.Barrie's Peter Pan.
I know he tackles this theme using different approaches, for example in the story the theme of growing up is divided into the inevitability of growing up (as seen by Wendy) and never growing up (as seen by Peter Pan, his shadow and Mr. and Mrs. Darling).
I would love to hear some ideas about how I can tackle this theme and write a good and long essay concerning this.
I was probably also thinking about giving a little background information about the author and his the tragedy that happened to his brother and his encounter with the young boys in the park.
Thanks in advance!

I'm assuming this is for some sort of secondary school/high school level essay, right?

You've got enough to work with just with the dichotomy between Wendy and Peter to work out an essay. Some directions you might think of is how ageing is romanticized in the text, and ultimately what kind of message is Barrie trying to get across. Is growing up a good thing, or a bad thing? Does the story soothe our concerns about ageing?

The theme is there, what you need now is a thesis about what exactly Barrie does concerning that theme.