The work of children's illustrator Nick Sharratt is instantly recognisable for its wonderfully vivid colours and cheery, plump-cheeked figures, as well as the impressive array of people he's worked with. Parents on bedtime story duty or observers of what their kids are reading might know him from his illustrations for Jacqueline Wilson, or his collaborations with Julia Donaldson and Giles Andreae for a younger audience. The Shark in the Park series, however, is written and drawn by Sharratt himself, so it's designed to appeal to his youngest demographic of all.

As such, the stories themselves are light on plot, and so this theatrical adaptation from Scots company Nonsense Room (the company's Julie Ellen and Bruce Strachan adapt and direct) with the Macrobert Arts Centre and ABA international touring has to combine all three books to reach an hour's worth of storyline.

We begin at bedtime with young Timothy Pope (Amy Robinson), who can't sleep because it's his birthday; he menaces his dad (Paul Beeson) all night, until he's taken to the park the next day, where his overactive imagination mistakes all sorts of innocuous, black-pointed objects for a rogue shark.

Timothy's not finished when he gets home, imagining the same sights in his room while he can't sleep (Shark in the Dark) and the next time he visits the blustery playground (Shark in the Park on a Windy Day). The warm and likeable trio of actors onstage – Zoe Halliday completes the ensemble – tell a very simple story, but the pop-up effects on Peter Horsburgh's set, the lively songs composed by Matthew Brown and Simon Beattie, and the repetitive joys of yelling 'there's a shark in the park!' in panto fashion make this a show with an irresistible pull for little children.

Festival Square Spiegeltent, Edinburgh, until Sat 6 Jan.