One day my friend brought her five month old granddaughter Jenny to coffee. Jenny wanted to play with a phone, but kept opening apps, making phone calls, clicking banner ads, etc.
So... I made an app that was interactive, but where a Jenny couldnt do anything disruptive like deleting apps or placing phone calls.
And... if you temporarily disable the Home Button with Apples Guided Access setting, the home button wont let anyone out until you say its O.K.