Sean Anders previously wrote and directed films like Daddy’s Home and Horrible Bosses 2, so you’d be forgiven for thinking that Instant Family would be a similar slice of shlocky farce. Rose Byrne and Mark Wahlberg star as Ellie and Pete, a suburban couple who flip houses – a metaphor for their commitment-free approach to life. But then they try to apply that life working philosophy to a more meaningful vocation – fostering a child.

However, when the couple meet spirited 15-year-old Lizzie (Isabela Moner), they realise she has two younger siblings also in the system; sweet and nervous Juan (Gustavo Quiroz) and the adorable Tasmanian devil youngest, Lita (Julianna Gamiz). Suddenly, this well-intentioned but clueless couple have three children with already-formed personalities, habits and trust issues. All parenting may be a madcap adventure, but these two are suddenly navigating without a roadmap, compass or any understanding of the terrain.

It’s a situation ripe for Anders’ brand of comedy – but based on his own experiences, there are some gorgeous moments of emotional honesty. Byrne and Wahlberg are winsomely overwhelmed, stumbling over their own good intentions and struggles. What happens if they start thinking of the children as their own? What happens if they don’t?

Moner is fantastic as Lizzie, who is smarter and more jaded than any 15-year-old should be, and gets angry and confused when she starts feeling safe and loved in her new home. When will it all be ripped away, like all the others?

But Instant Family wants to be both smart and silly, melancholic and upbeat, and struggles with finding the balance. Montages set to pop songs undermine difficult moments, and some jokes – like a random, superfluous Joan Cusack cameo – feel like desperate attempts to give the film an extra comedy stamp. It’s a sweet if stumbling film, though it hints at Anders’ emotional intelligence. If he trusted himself to let that shine onscreen, it could be a game-changer.

Directed by Sean Anders. Starring Mark Wahlberg, Rose Byrne, Octavia Spencer, Isabela Moner, Tig Notaro. 119 mins. In cinemas now.