There is a feature in iOS 8 that I am sure most parents don't even know exists. It is called Guided Access and it is a parent's best friend. Once enabled the current app is locked. Your kid cannot use the volume, sleep or home buttons until the set time limit ends or you disable it.

How To Enable:

  1. Launch Settings
  2. Go to General
  3. Go to Accessibility
  4. Go to Guided Access
  5. Toggle Guided Access to On Position
  6. Set Passcode
  7. Toggle Accessibility Shortcut to On Position

How To Use:

  1. Launch Any App
  2. Triple Click Home Button
  3. Set Options
    a. Decide to Allow/Disallow the Sleep/Wake button, Volume buttons, Motion, Keyboard and/or Touch
    b. Set the Default Time Limit
    c. Click Done
  4. Circle Any Part of The Screen You Want to Disable
    (Example: Circle Purchase Button to Prevent Your Kid From Clicking)
  5. Click Start

At this point the app will stay locked until the time limit expires. Once this occurs, the screen goes dim and a message is displayed to let them know the time expired. If you want to disable it at anytime, you can triple click the home button and enter the passcode.

Hopefully this provides a little peace of mind and control for the next time you let your little guy play Minecraft on your iPhone.