The Lost Boys and Peter Pan want Henry to save magic… because magic is dying [in Neverland].” And that is a bad thing because…? “If magic is fading, maybe they’re getting older,” Gilmore guesses. “Then they can’t stay young forever in Neverland.”
I have a feeling that having filmed 7 or 8 episodes, Jared Gilmore would’ve figured out the reason why Pan wants Henry. So, I’ll take Jared at his word when he says the reason is that Henry needs to save magic. We saw a bit of this in 3×1 when Pan said the pixie dust was useless. While Pan certainly was testing Henry’s belief, I think Pan might actually have been speaking truthfully. Maybe PP has lost his belief and so he can no longer fly. I have a theory that Pan and the Lost Boys are stranded in NL. That is why we’ve only seen the Shadow, rather than PP himself, flying between NL and Earth.
I think that PP needs Henry’s figurative heart rather than his literal heart. You’ve heard the expression, “He’s full of heart” which means someone is full of life, confidence, courage, or in this case perhaps, belief. Probably, Pan needs Henry’s belief to rub off on himself and the other Lost Boys, which is why they’re playing games. In ‘Hook’ Peter had grown up and lost his belief, so he couldn’t imagine the food in front of him, but then the Lost Boys were full of imagination and the food they were pretending to eat suddenly manifested to PP when he allowed himself to believe again.
"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy