If only this had been available when my children were little. In Who Made God, Brian Smith sets out the tenets of Christianity simply and accessibly. The book is written chiefly to be read with children, starting with What is God Like? (or, "for people who like to use big words" The Incarnation), moving on to include The Three-in-One God (The Holy Trinity), The Inside Story (The Fall), The Big Surprise (Atonement), Jesus II (The Holy Spirit), and What Happens in the End? (Eschatology). It consists of a story about a family where the children are tussling with questions about God, and the answers emerge as the book progresses. Each chapter contains boxes with more complex explanations of the theological concepts involved (this reader learned more about the Trinity in minutes than in over thirty years), and a brief summary of the points raised, concluding with an activity for children, and suggestions for discussion.
Of course, my children are older now and clearly Know Everything, but I really do recommend this book to anyone with young children, who would like to be able to explain the Christian faith to them clearly and easily.