It's possible to set your iPad up to prevent children switching between apps - you can 'lock' the iPad to one app until you change it.
Go to settings, general, accessibility, the select guided access, and tap the switch to turn it on. Choose a numeric passcode you'll remember. Now when an app is open, triple click the home button. You'll be asked to enter your passcode, then the app cannot be closed until you triple click the home button and enter the passcode again.
You can also disable parts of the screen, for example if you want to prevent any settings being changed within an app, by drawing a circle around the part of the screen you want disable when you triple click to open the guided access settings.