Abe Forsythe is an Australian actor and director whose last feature was the satirical Down Under, about the Cronulla race riots – the ethnic violence that broke out in 2005 in a beachside district of Sydney. His new film is a dark but amiable and unexpectedly sweet-natured comedy on the umpromising subject of zombies. This is well-worked territory for horror and horror-comedy, but Forsythe makes it work.

Alexander England plays Dave, a waster and no-hoper who nurses dreams of stardom in the world of death metal. In return for crashing with his long-suffering sister, Tess (Kate Stewart), Dave is prevailed on to be one of the helpers for a school trip that Tess’s young daughter is going on to a safari park, where there will be a celebrity appearance by a creepy TV kids-show comedian called Teddy McGiggle (Josh Gad). Dave had initially no interest, but he has pathetically fallen for the kids’ elegant, beautiful teacher, Miss Caroline (Lupita Nyong’o), who will also be going on the trip. So this unlikely school group sets off, little knowing that the safari park is next door to a military biological-weapon testing facility, where there is a very real possibility of a zombie outbreak.

The pure silliness of this idea is enjoyable. The children give guileless performances, and Nyong’o gamely plays the broad comedy for all its worth. As for the zombie action, with the dozens of extras shambling along, doing the traditional stiff-armed-head-on-one-side-face-covered-in-gore routine – well, it’s pretty familiar, and perhaps this kind of thing simply can’t work without a side order of comedy as an excuse. But there’s a nice rapport between Nyong’o and England.

• Little Monsters is released in UK cinemas and on Sky Cinema on 15 November.