Jimmy never seems to have much patience. This seems to be a pretty realistic story. Remember though, it's his story, so he gets the final say in these things. You can continue to build his understanding of story building as you read stories written by others, pointing out, for example, that everything in this story is realistic, or that the character's behavior in a certain situation is believable for this reason. When my children were smaller, we gathered together selections from everyone's creative writing files and made an anthology.
Kids love to see their work treated like real books.
You can put the story in a school report cover, fully illustrated, of course, and place it on your bookshelves for everyone to read. With desktop publishing, you can make a very professional anthology of your favorite family written stories. Mail their stories to Grandma and Grandpa. Whatever it takes, get their stories out in public to someone besides you. There are even writing contests for children if they are mature enough to handle the competition.