Have you tried Storybird.com yet? It is a fun online site for kids to use to write stories/books. The site provides sets of illustrations, the student chooses pictures from a set and writes a story to accompany the pictures.
My students last year liked it, and I liked that it was an easy way for them to share their writing with me, their classmates, parents, or grandparents!
On this site, you create a class and enter your students names. Students then use their username and password to access the site.
It was a great option for my students to use during their independent writing time. It also allows for the teacher to create an assignment for the class. I would recommend that you check it out as an option for the next school year!
Thinking of writing, you still have time to link up and share a mentor text to use when teaching students about voice.