For the Spanish Honor Society at the high school where I teach, our biggest and best service project has been a summer Language Camp for kids ages 4-10. Since our school happens to also have a French Honor Society, we decided to pair up and work together. You could also do this camp with Spanish only (or German only, or Italian only...) and it will be awesome either way!
This printable guide goes through the steps you need to take for a successful Language Camp at your school. I included a PDF format (for easy printing) and a Word document (with editable templates). I also included the 2015 and 2016 camp curriculum and parent letters that we used at our own school.