I never let the kids near any transformer controls, always worry about the risks if they get into the wires.
I have 7 LionChief engines with remotes.
I bolt then down to the fence with photos of the engines they are running with a plastic bracket to keep them from turning the speed control too far and breaking it ( from experience)
Using the LionChief remotes allows them to run trains without touching any wires.
I power the tracks from Transformers and set them so the trains will not run to fast when the kids turn the LionChief remotes to full throttle.
Here is my latest set up but similar to what I attach to the fence for several shows each year. Click on photos for a larger view. Wood either side of the LionChief controller and screws on sides to keep them from shifting, zip straps to hold them in place. Room to slide a screw driver down the side to turn controls on and off. I have the sound buttons covered as when kids have all 7 trains with bells on drives you nuts. And they cannot tell which engines have sounds. I have a little sound engine in front of each controller if they listen close and push top of train they hear all sorts of sounds from that train.