There are two control options with the PE controller. One is the push button option, the other is a switch using the original handbrake unit itself. If the concern is the switch may be pushed , go for the handbrake option. It will look identical to what is standard and unless the grandson has a predisposition to high speed handbrake turns, will present exactly the same risk as what you currently have.
I believe you have to specifically request the controller for the hand brake option ? Ask PE to confirm. The board seems to take both types of inputs so I am not sure what the difference is other than the switch.