I don’t think we will use the 3.5MM mono plugs for this mod. I do see the benefits of multiple ports for easy configuring to child needs.
I believe we are going to forgo the big switches and do a 3D printed lever on a handle bar that activates a limit switch. Takes little effort to engage lever - weight of arm/hand easily engages the switch.
We can rotate the steering wheel 180 for child with shorter arms so handle bar is closer to the torso. If we have the need for a button on door panel or head rest area we will use a large button or 60 MM button and directly wire it in.
It was a good project for the kids to design a handle bar and 3D print the parts. They likely will have a couple more revisions as they need to encase the hardware and reinforce some points. We will definitely share the pictures, CAD, and STP files with the GBG community.