Google has created an online program called "Be Internet Awesome" for grades 3-5. There is an online game for students to play titled "Interland". This article from Fortune.com tells more about the background of the program and how it works. On this site there is also a trailer that gives some great visuals. There is also an educator lesson guide so you can actually connect with your students and physically teach about different components of internet safety, instead of just sticking them on a game. The plans are laid out very nicely. This final link has tons of resources for you. It has links to the lesson guides, posters, parent information and more!