Here are the ratings of of the current Cosmere books/Series.
PG-Elantris and the Emperors Soul, Edge Dancer
PG-13 Younger-Stormlight Archive, Mistborn Era 2, Silence Montain and the Forests of Hell, Mistborn short stories, Sixth of Dusk.
PG-13 Older-Mistborn Era 1, Warbreaker
I also think that what you read to kids and younger people depends on what you are comfortable with and with the child's maturity level. By the time they are in 7th and 8th grade, I think they can read most of the Cosmere except Warbreaker. That is a book that should be reserved for High Schoolers.
