There is simply no reason for a live-action adaptation of the interactive children's cartoon Dora the Explorer to be good. And when we add in the ugly wrinkled that the beaming seven-year-old of the show has been aged up to an improbably innocent teenager forced to go to public school for the first time, I should say that there's simply no reason for it to be tolerable at all.

But these concerns are the concerns of cynical adult wisdom and pessimism, and therefore of no concern whatsoever to Dora and the Lost City of Gold (for that is the live-action feature's title), a film uncommonly, even eerily devoid of cynicism or sophistication. It's such a profoundly square movie, and that's its most magnificent strength: we have for the first time in a long while - the first time in 2019, at any rate - a theatrically-released family-friendly film that is entirely committed to reflecting the sense of gee-whiz wonder that it hopes to instill in its preteen target audience. It doesn't talk down, doesn't smirk (or, at least, not after its first 20 minutes or so), doesn't throw in some sotto voce sex jokes to keep the parents in the audience amused. It is an exceedingly lovely, gentle thing.

The basics of the plot are a little different than what I've suggested: so yes, there's a girl named Dora (Isabela Moner), who has made it to the age of 16 or 17 after being home schooled by her parents (Michael PeΓ±a and Eva Longoria), a pair of explorers who've spent their professional careers in the Amazon. Time spent in the company of nobody but wild animals - notably a curious monkey she calls Boots - has left Dora without a shred of guile or doubt; but she is full of the teenager's cocksure estimation of her own skills, and manages to almost kill herself while exploring some ruins. That's enough for her parents to decide that she had better leave the jungle for a bit, and so they send her off to Los Angeles, to live with her grandmother (Adriana Barraza) and former best friend, cousin Diego (Jeff Wahlberg). Here she marches into public school, head held high, and becomes the instant target of all the cruelest mockery you could imagine from a film that refuses to contain even a single swear word. But she's so confident in knowing who she is that even though she knows she's being insulted, she refuses to let it hurt her.

This isn't the plot, actually. The plot is that, on a field trip to a history museum, Dora gets kidnapped by the smuggling cartel that has unsuccessfully tried to find her presently-missing parents, and three fellow outcasts inadvertently get kidnapped with her: Diego, widely-loathed class president Sammy (Madeleine Madden), and flop-sweating geek Randy (Nicholas Coombe). Back they go to the Amazon, where Dora's indefatigable attitude keeps the other three alive through one peril after another, as well as the totally hapless adult Alejandro (Eugenio Derbez), a colleague of her parents.

You can fairly neatly slice the film into its short prologue, depicting Dora as a bright-eyed child played by Madelyn Miranda, the opening act that sends Dora to L.A. and then brings her back, and the "Indiana Jones for wee folk" adventure of the remaining hour and some. And, if I am any judge at all, the opening act is the only real rough patch in the whole. This is largely because it's then and only then that the film operates as what it was easiest to suppose it might be: a slightly mortified cringe comedy about the go-getter Dora constantly making an ass of herself. It's here, and only here, that the film openly mocks its source material (Dora turns to the camera and invites us to practice Spanish, asking "can you say delicioso?", at which PeΓ±a does a big triple take); it's here, and only here, that it seems to regard her as an alien goofball who's too far gone to understand basic social interactions. And this is cheap and easy humor, though not without its charms, which are largely the result of PeΓ±a and Longoria being so impeccably straitlaced, and Moner being so wide-eyed and sugary. There is a long joke (too long, by half) in which PeΓ±a performs an a capella version of early-'00s club music, and one gets the sense that director James Bobin and editor Mark Everson let it go on at such length largely out of awe that Longoria and Moner were able to watch their co-star pulling such strange faces for so many endless seconds without breaking character for even a fraction of a second. The point being, the three leads commit to their parts with an earnestness that admits for no trace of embarrassment, and it reflects well on the movie.

It also gives us a taste of what will, at all points, be Dora's extremely obvious secret weapon, Dora herself. Moner's performance is a remarkable act of skill and trust: the actor, 17 years old at the time of filming (which makes her about one year younger than Dora the Explorer itself, if you were looking for something that would make you feel like your mummified skin was crackling against your dusty bones), opens up her face to be as big and moon-like as possible, reciting some unfathomably bubbly and daft dialogue with a giant, toothy smile, revealing a fearlessness about looking like a silly buffoon that is most uncommonly rare in the adolescent human. She's playing a live-action cartoon in the most direct sense, and there's never a moment of self-awareness about that; she exudes a confident, smiling energy that puts me in mind of nothing less than Sally Hawkins's star-making turn as the warm, candid optimist of Happy-Go-Lucky back in 2008.

I mean, James Bobin is no Mike Leigh, let's be clear about that. But he is more than capable of keeping things bright and warm, and encouraging his cast to keep things slight, sweet, and silly; Dora is so gentle and sincere that it makes the director's work on 2011's meringue-weight The Muppets look positively toxic. This leads to at least one genuinely satisfying surprise, in the form of Derbez's performance; I typically find him shrill and exhausting, but he turns out to have exactly the right energy to play the useless, pratfalling grown-up in a kids' adventure movie. It's unfortunately the case that Moner's other prominent co-stars, the three other teens, aren't particularly interesting at all, and their uncertain, shticky line readings and reaction shots serve as a contrast that ably demonstrates just how good Moner is at channeling the simple openness of childhood.

With that lead performance as its anchor, Dora proves to be a very lovely, good-natured kiddie flick, one that's heavier on playful entertainment than thematic resonance, though it does nod towards its roots in educational programming now and then: there's a crisp, brief, child-sized critique of colonialism in a couple of moments, and practical guide to surviving quicksand in one of the not-very-frightening thriller setpieces. Mostly, it's just about having fun with the silly logic of kids at play - Benicio Del Toro plays a talking, anthropomorphic fox (played, like the monkey, by a mildly terrible CGI effect), and this is treated without a hint of surrealism - and providing a fine, admirable role model as the vessel through which all of that play is funneled. There's basically nothing here for adults, but there's also nothing saying there should be; preteen kids need well-built popcorn movies too, maybe more than anybody, and Dora's warm vibe is exactly what I'd want to share with the children in my life, if I had any I was responsible for.