Especially the Amazon freetime settings that let you control how they use it. This section of Amazon is great for free apps and interactive books for little kids: http://smile.amazon.com/s/ref=lp_11350978011_nr_n_9?fst=as%3Aoff&rh=n%3A2350149011%2Cn%3A%212445993011%2Cn%3A11350978011%2Cn%3A9408582011&bbn=11350978011&ie=UTF8&qid=1448654408&rnid=9209898011

Our public library lets us checkout kindle books for free and they have a lot of them for older kids and young adults.