The Peter Pan elements I can think of is, children discovering a fantasy-type world, a child having supernatural powers, Saoirse being a selkie ( I had no idea what a selkie was before seeing this movie, so it was cool to learn about that!), a boy losing a mother, though in different ways, Ben’s mom died, but Peter’s mother forgot about him.
This is not a Peter Pan element, but a Llewelyn-Davies boy element, Ben seems to have a fear of water, similar to Michael Llewelyn-Davies. But Ben manages to overcome his fear, though Michael of course, never did!
You can probably think of more elements than I can, but those are the only ones I could think of!