Given the current attitudes in what is now largely Republican Tennessee where this film is set, it’s somewhat surprising to see such a sympathetic depiction of the travails of a family of economic migrants from the southern hemisphere who come to America seeking their fortune. Gullibly believing that the offer of a job is real and facing economic hardship in his homeland, the somewhat deluded father hauls his wife and six children (seven if you count the one the wife is carrying), across the border where they only just escape scrutiny from suspicious border guards. When the promised job falls through, the parents are compelled to put the underage children to menial yard work and cleaning jobs so that they have enough to pay for basics such as food, beds and – eventually – petrol for a car given to them by a member of their church. Because they’ve overstayed their visas, they can only take cash-only employment, and they must rely on further charity to pay the exorbitant medical bills when the mother gives birth. The father refuses to return home, even when his family down south offers to foot the travel costs and the mother, home schooling the kids, persuades the children to believe it’s God’s will they stay where they are.

Of course, what makes this film different from scores of other dramas about migrant suffering, most of which end in tragedy, is that the family at the story’s heart are white Christian Australians. And given this is produced by a faith-based production company and directed by one of the family themselves, everything comes up roses in this supposedly true story, including a Christian-country-gospel recording career. The father, David Smallbone, is played by one of his sons Joel (who himself is played by young actor Diesel La Torraca); by the time the happy ending rolls round he’s learned to check his pride, thanks to a firm talking-to from his wife, Helen (Daisy Betts), the always smiling, perpetually upbeat, unsung hero of the title. The whole shebang is so sugary it should come with a warning for diabetics.

Perhaps mindful of the need to maximise the film’s appeal to as wide a demographic as possible, there’s no mention of the anti-abortion activism of big sister Rebecca, who went on to record under the name Rebecca St James. (She is played here by Kirrilee Berger). Instead, the film is as bland as whole milk, but admittedly competently made. The songs are pleasant enough to listen to and the younger actors perform well without seeming too pert or excessively cutesy.

• Unsung Hero is in UK and Irish cinemas from 14 June.