There is no better, more inexhaustible well of material than the family.

And Nat Faxon and Jim Rash - actors turned writers turned directors - are proving quite adept at drawing from that well.

The Descendants, for which they won a Best Screenplay Oscar, focused on a man forced to connect with his daughters fully for the first time, while his cheating wife lay in a coma; with George Clooney in the role, the result had humour and pathos in equal measure. The Way Way Back shifts the perspective to that of a teenager, but that delicate balance remains very much in play. This is a lighter film, but immensely satisfying.

We first meet 14-year-old Duncan (Liam James) in the back of a station wagon en route to a quasi-family vacation with his mother Pam (Toni Collette), her boyfriend Trent (Steve Carell) and his daughter Steph (Zoe Levin). The fact that this is a forced holiday is immediately evident from the direction Duncan is facing - backwards, towards home. It's also immediately clear that Trent is a nasty piece of work.

Trent asks the boy what score out of 10 he would give himself. The answer is a modest six; Trent insists that he merits only three. That's a great way to start a holiday, the aim of which is to gel as a family unit. The torturously introverted lad looks as though he's about to be sent to Alcatraz.

Their actual destination, Boston's South Shore, seems to be populated by appalling parents. A little like Collette's character in About A Boy, Pam is well-intentioned, but too absorbed in her own well­being to properly consider her son's; their neighbour on the beach (Allison Janney) is another good soul but terrible mom, constantly teasing her son whose lazy eye "makes people uncomfortable". There's no sign that Trent did a better job with his daughter than he currently is attempting with Duncan.

All the kids must find their escape routes. For Duncan, it's Water Wizz, the local water park, whose charismatic manager-cum-slacker Owen (Sam Rockwell) becomes a surprising friend and mentor. Sensing the boy's loneliness, Owen gives him a job at the park, introducing him to the small, personable team managing the pools and chutes; slowly the man's confidence rubs off on the boy.

Newcomer James is light years away from the polished, factory-line kids Hollywood usually produces; so normal, in fact, that he's difficult to describe, and therefore perfect as an "Everyboy" finding his own way in life. His character doesn't say much, so that when he does open his mouth we're keen to listen. In contrast, Owen won't shut up, issuing a murderously funny stream of consciousness. But there's method to the character's seeming abandon - for his own part, smoothing over the knowledge that he's coasting, avoiding commitment; but also chipping away at the boy's defences, drawing Duncan out of himself. It's a lovely performance by one of Hollywood's coolest, smartest actors.

Carell is a good sport to provide the villain of such a charming movie. It's not surprising that the comedian is so effective: his usual comic persona is founded on anal retentiveness - all he's done is skimmed off the vulnerability.

The film reminds me a little of Adventureland, from 2009, a coming-of-age tale in an amusement park. There the kids were a little older, the humour acerbic; The Way Way Back is a gentler affair, eccentric and silly, and a ray of sunshine amidst the so-called summer blockbusters.