I think the kids (and adults) will get a much larger charge of actually using the transformer controls to run the train and modulate the speed, etc. Have ing a push button to run a canned sequence gets pretty boring very quickly. You're also creating a lot more work wiring horn and bell buttons for twelve tracks!
IMO, the KISS principle is in play here, a couple of hidden variacs to limit the maximum voltage, and the controls on the transformers function as designed, job done.