Idioms are a great way to incorporate culture into your classroom. Here's a list of 27 I use daily in my elementary Spanish classes. Mundo de Pepita: Spanish Idioms for the Classroom- Comprehensible Input in Context
Fun for elementary Spanish. Even if it's not a required subject I think I would still try to incorporate it because kids learn faster and retain that information better than adults. Maybe have extra credit quizzes on it or something.
This is a short TPRS story for beginning Spanish students. It has a limited vocabulary of less than 25 words, many of which are repeated throughout the story. I have set the age as 5th through 9th grade, but this story could be used with beginning students of any age (I have taught elementary, middle, and high school Spanish).I use this story as part of a unit on weather.