V.S.
Kindles come with parental controls that not only prohibit access to the internet, but also can be set to limit time on the device for reading or, if you have a kindle fire, for games or other media. Look up "free time on kindle" for more information. Also, if you're only getting a reader and not a multiuse tablet, the kindle is very affordable.
Eta - a lot of the kindle settings and downloads can be controlled from amazon site without accessing the kindle itself.