The ability to add a second user profile was added to tablets in Android 4.2, and it's gained even more granular functionality in Android 4.3 with the addition of "restricted profiles." In a nutshell, this lets you choose which applications that restricted user can use.
It's not quite a full-functioned kids mode, and there still are a couple things to watch out for. But for basic account compartmentalization, it works pretty well.
Let's dive into it and show how to use the new "restricted profile" feature in Android 4.3.