John Spencer, author and educator, has created a playlist of Maker Challenges and Design Prompts for Kids. These ideas could be a great tool to have in the case that you have extra time in a class, or the students finish earlier than expected. Most activities require little to no supplies and are built for the students to engage in creative thinking. Pick a few that you are comfortable with and allow the students to choose which they would like to complete. Time permitting, they could share their work with their peers.