I do recommend this "mock confession" model. I also suggest the idea of filming a video with your child--this highly motivated Leah to learn! She told me the next day that she is READY for her First Reconciliation! The main thing to avoid is the idea of checking off a "grocery list." When you say you are sorry to someone you hurt, you come with contrition and sorrow. These are the most important elements for us to bring. God does the rest.
Here are the words. The words in bold are the things you can actually say (the actual Rite does not call for these words, but they are the customary form and can help to get over nervousness):