"How old are you, Peter?" It's a good question. With his ruffled hair and his receding hairline, the boy who wouldn't grow up looks well into his forties in Sally Cookson's playful rendition of JM Barrie's adventure story. That one choice turns his tale on its head. Paul Hilton's Pan is an adult in all but his attitude. It's not that he can't grow up, but that he won't.

After her revelatory Jane Eyre last year, Cookson tunes into the symbolism of aging and adulthood in Barrie's classic. With its ticking clocks and near death experiences, it's all there for the taking, but Cookson teases it out in two ways at once: as a critique of contemporary culture, and as a celebration of theatre itself.

More than any other art form, theatre relies on our inner-childishness. It needs us to play along, and Cookson serves up a big slab of make-believe: a junkyard crocodile and ribbons for rivers. When her characters fly, they do so in plain sight: winched up, via pulleys, on (cough) "fairy strings." The cast work as counterweights, the harnesses are on show. It's up to us to see flight.

That ambiguity is matched by ambivalence. Cookson sees both the necessity and the horror of aging all at once. Hilton's Pan is both a marvellous mischief and a pathetic manchild, and, next to him, Anna Francolini's Hook becomes a spectre of old age and decay. One's terrified of death, the other of maturity, but neither has an adequate answer.

Squeezed into his ever green suit – the boy who wouldn't grow up has, it seems, grown out of his clothes – Hilton cuts a rakish figure. There's a weathered boyishness to him, the spring in his step at odds with the gravel in his voice. In fact, he's not a million miles from that old Babyshambles Pete Doherty, still swashbuckling and slurring his words.

His Neverland is, essentially, one big squat party going straight on ‘til morning and, surrounded by Lost Boys in hipster beanies and retro jumpers – the generation committed to childishness – Hilton becomes their ringleader. He's a familiar figure: the wayward hanger-on, too old to be kicking around with kids. When he pushes them to play mothers and fathers, it's more a mockery of adulthood than a mimicry of it.

On the other side of the island, Anna Francolini's Hook pulls on a black wig and a corset to hide her old age. A bald, frail old thing with silver teeth to go with her hook, she is a spectre of old age and death, but she's more creepy than she is villainous.

This, perhaps, is the problem with Cookson's production. For all it smarts, it struggles to stay airborne. The magic of its first moments, when Benji Bower's spine-tingling music leads us into a flight across the whole solar system, doesn't sustain as the show reverts to more bungeeing and bouncing with diminishing returns.

There are great flickers of playfulness within – Felix Hayes and Ekow Quartey are never less than delightful – but as a whole the ensemble struggle to compete with the size of the space, and they're not helped by Michael Vale's bare-stage design which rarely animates it and often leaves them adrift. Saikat Ahamed's Tinkerbell – a fierce little firefly of a fairy with a sharp tongue on him – is a measure of how hard some have to strain, and he's so irritating it's tempting not to clap him back to life.

The bigger problem, though, is its politics and Cookson isn't radical enough. Having problematised Peter, she still lets him win the day: this rakish, slightly repellent anti-hero. Madeleine Worrall's Wendy might resist the roles she's pushed into – the sensible girl forced to mother lost boys – but she still ultimately ends up conforming to them. If that's what growing up means, maybe its better to stay in Neverland.

Peter Pan runs at the National Theatre until 4 February.