Donaldson plans to promote music and drama and champion libraries during her tenure
Donaldson becomes the seventh laureate, and was described as "a wonderful choice" by one of her predecessors, the poet Michael Rosen.
"She has written such accessible and brilliant books and she's so clever and funny. She believes in taking her stuff out to kids, and sharing it," he said.
Her immediate predecessor, the illustrator Anthony Browne, left her an open letter urging: "Do everything you can to support libraries – God knows, they need every bit of help they can get nowadays." Everyone, he warned, "will pay the price in the long term" for school and public library closures.
In fact Donaldson, who lives near Glasgow and is the first Scottish-based laureate, needed no urging. In recent months she has flung herself into the campaign to save libraries, leading a protest meeting at the Scottish parliament, signing petitions, and turning up at readings in libraries in Scotland and England.
She is promising even more ardent efforts in her new role.
"I'd love to do a libraries tour from Land's End to John O'Groats," she said. "The children who would come to events in libraries would have been briefed beforehand that they would come to perform something to me, so the first 10 minutes of each session they might perform a class poem they had written or act out a favourite picture book.
"Maybe I'll be able to talk to the minister of culture and persuade the government to have some kind of overall plan because at the moment I feel all the library cuts and closures are very piecemeal, so I'll do what I can," she added.