Hmmm, had a play with my own iPhone 7 Plus and can clearly see within restrictions there is no way of stopping calls outgoing/incoming
Maybe not so good idea
The only time she is going to have it is when she's out with you playing the game right? So this shouldn't be a worry. You can also put it on do not disturb mode if you don't want calls coming in. Or hide the phone icon in the back page of a random folder if you don't want her accidentally calling out.
