I don't have an I-PAC/4 - but the best suggestion I have seen for it was to have a dedicated Pause button and have that activate any of your Shift functions such as Exit, Tab, etc.
That's how I have mine set up.
Press and Release makes the cab Pause.
Press and Hold allows the other buttons to do shifted functions.
I think the best idea for a kid cab is a toggle switch inside the coin area, or on top of the machine, that allows the shift function to be turned off.
There aren't any shifted functions they need access to, and the risk of them messing up the software is too high.
You can set up a dedicated exit button to allow them to drop back to the front end.