Children’s books are, like children, unruly things. Eccentric or transatlantic spellings and quirky punctuation have been kept as far as possible faithful to the edition under discussion. The odd particularly extravagant outburst of random early-modern italics and capitalizations (looking at you, John Newbery) are per the originals, too.
As for Peter Pan, the tangled publication history through which he came into our imaginarium – book section; play; novella; novel; revised and retitled novel; and so on – means keeping the title of the works in which he appears straight is about as easy as ruling on how to spell Neverland. That’s the devil in Peter. The fullest prose version – Peter and Wendy, later Peter Pan and Wendy – now mostly goes by Peter Pan.