How do you make a football out of an inflated condom, a plastic bag and a piece of string? Pay close attention to the opening scene of this colourful postscript to World Cup 2010 and you might just find out. Dudu (Eriya Ndayambaje), the Rwandan boy at the centre of Africa United, gives a Blue Peter-style demonstration, accompanied by a bravura speech about the benefits of prophylactics. It’s the kind of blatant propaganda that won’t amuse hard-line Catholics.

Writer Rhidian Brook has structured the story of orphan Dudu, his younger sister Beatrice (Sanyu Joanita Kintu) and middle-class soccer fanatic Fabrice (Roger Nsengiyumva) as a road movie. It begins in a village in Rwanda, where Fabrice’s “silky skills” catch the attention of a Fifa talent scout, who invites him to audition for the World Cup opening ceremony. Before you can say Cesc Fabregas, Dudu has bundled his “team” onto a bus, for the trip to Kigali. But their destination isn’t the Rwandan capital and they end up in Kinshasa (Democratic Republic of the Congo). Dudu’s clanger is a game-changer that turns their adventure into a gruelling 3,000 mile trek to Johannesburg’s Soccer City.

When Hollywood takes a trip into the Dark Continent — The Last King of Scotland, The Constant Gardener, Disgrace — we often end up with movies that are filtered through the consciousness of white people. Africa United, the feature debut of director Debs Gardner-Paterson, is a UK/South Africa/Rwanda co-production, shot in three countries and with the emphasis squarely on the experience of young black Africans. Those hoping for a glimpse of Angelina Jolie or David Beckham hugging cute black babies should look elsewhere.

The film-makers wanted to get beyond the stereotypical portrayals of a continent ravaged by poverty, violence and disease. Dudu is both a self-appointed leader and a flamboyant story-teller who bolsters his companions with a parallel narrative about their journey, which unfolds in a series of animated sequences. Brook’s screenplay is strong on the kind of topical banter — football and Barack Obama – that will appeal to young audiences, who will also share the travellers’ sense of wonder at the breathtaking landscape. Africa United rolls along with the help of Sean Bobbitt’s sparkling cinematography, Victoria Boydell’s innovative editing and a bold mix of African and European music.

But there are also serious issues here, highlighted by the group’s stop at an HIV testing centre, and encounters with teenage soldier Foreman George (Yves Dusenge) and former sex worker Celeste (Sherrie Silver). This is where the limitations of the actors – particularly the boys playing Dudu and Fabrice – become painfully obvious. Their delivery is wooden and they lack the subtlety to draw us into the traumas experienced by their new friends. Similarly, there are a couple of explosive scenes – one involving a thug played by Tsotsi’s Presley Chweneyagae — that fail to generate any sense of peril. At least Dusenge wordlessly conveys some of the inner turmoil resulting from his own “rumble in the jungle”, but Ndayambaje’s relentless chirpiness soon begins to grate.

Rabbit-Proof Fence and Slumdog Millionaire have their flaws, but they also leave audiences with strong feelings of revulsion, pity and disbelief at the cruelties and injustices inflicted on children. Africa United aims for a lighter approach, which is no bad thing, but it also focuses exclusively on a journey, with no subplots or substantial supporting roles for more experienced actors. That’s a risky strategy when the performers are not skilled enough carry you through the emotional rollercoaster that such an extraordinary trip must entail. There are underwritten cameo parts – Fabrice’s mum, a saintly nun, a gruff South African security guard — that might have given the film more dramatic weight if they’d been given more room to breathe.

Africa United packages its messages about teamwork, loyalty and friendship in an engaging, family-friendly plotline. No-one should leave the cinema without knowing how much fun you can have with an inflated condom. But like the England team at the World Cup it lacks the depth or quality to make it all the way to the top.

(Africa United is showing as part of the BFI London Film Festival, on 17 and 20 October.)