If you lend your child a miniature computer like nexus 7 or Galaxy Tab 2, they easily find some offensive sites and material. So you need android parental control app to monitor your kid's activities and give them limitative rights on the tablet. There are some great parental control and monitoring apps on the Google Play store.
* Kids Place
The app restricts babies, toddlers and teenagers to apps you have approved on custom home screen and protects your personal data. It can also disabe all WiFi signals, and configure specified amount of time. Now I am able to totally relaxed leaving my N7 to my daughter with free time.
* Funamo Parental Control
Funamo does turn tablet into a safe device for kids, and works flawless on Android 4.1 Jelly Bean. It features safe browsing on Chrome browser, such as highly robust internet filtering and safeSearch with Youtube videos and Yahoo, and also protectes Settings and store, allows you to setup school-time and log the device's contacts, calls and applications.