For parents and others handing iOS devices over to kids, it might be wisest to lock down certain features so that children don't stumble across things they shouldn't, or accidentally wreak havoc upon your own device. Here's how.
Keeping your iOS devices permanently out of the hands of your kids is probably a losing proposition, but you can take a few simple precautions to make sure that your children don't get access to things they shouldn't have.
The first step is to launch Settings, and navigate to the Restrictions menu under General. Tap the Enable Restrictions button, and you'll be prompted to enter a four-digit passcode--you might want to make this different from your device's own passcode, if your kids happen to know that one.
Once you've entered and confirmed that code, you can selectively disable a number of built-in features. For example, you can turn off Safari if you don't want them to access the Web--that will not only remove the Safari icon from the home screen, but will also prevent them from opening URLs from other apps in Safari. (Be aware that apps with their own built-in browsers won't be disabled, though.) Likewise, turning off access to the Camera (which also deactivates FaceTime) will prevent many third-party apps from taking pictures--though it won't prevent launching the Photos app itself.
In addition, you can disable access to the App Store, iBookstore, and iTunes Store, as well as preventing your kids from deleting apps from your device. You can also choose whether they'll have access to Siri, and whether Apple's intelligent assistant will block out explicit language or not.
The allowed content sub-section uses common ratings systems to let you choose what locally-stored content is available to your kids. So if you've downloaded an R- or PG-13-rated movie, you can prevent tots from playing them back. Likewise for music & podcasts, TV shows, ebooks, and apps.
You can also deactivate in-app purchases to avoid having your kid rack up real-world charges in their favorite games, as well as specify whether or not to have a 15-minute window in which in-app purchases can still be made without re-entering your iTunes password.
If the device resides permanently in the possession of your kids, you might be concerned about what kind of information third-party apps have access to. A privacy section lets you choose which apps can get access to location information, as well as contacts, calendars, reminders, photos, Bluetooth sharing, Twitter, and Facebook. In many cases you can also specify whether a restricted user can make changes to these settings--for example, allowing Facebook access to a newly downloaded app.
You can also lock down other systems, including preventing your kids from adding or removing--accidentally or otherwise--your accounts in Mail, Contacts, and Calendars; altering settings in Find My Friends, if installed; and changing any volume limit that you've set.
Finally, Game Center controls allow you to disable multiplayer games or prevent your kids from adding new friends on the service.
If you decide you don't need restrictions anymore, you can always turn them off by returning to the Restrictions section, tapping Disable Restrictions, and entering the passcode you created.