Having a middle grade character want to be part of this is a great idea. If parents say no, what child doesn't want to do something? I'm not sure what the actual number of children involved in the battle was, but it is an intriguing premise.
Courageous is a quick pick for reluctant readers who need to have a book about World War II for a project, but are not really interested in the topic, but also for avid fans of this military conflict who have not read enough about Dunkirk. It has very nice notes and glossary at the back, and is told in simple, direct language. The cover is appealing and the story action packed. Hand this to readers of Sherman's military series, Spadlin's Prisoner of War, Gratz's Grenade, or the work of Dean Hughes.