What brand&type of track switches are you using?
If you are using track switches with the non-derail feature you can (at least in part) let the switches pick the route. When entering a switch whose position is such as to derail the train such switches automatically throw to permit the train safely through.
You can easily gang switches such that one remote-control push will throw two or more switches and between this and the non-derailing feature you can make it as easy to operate as you wish.
Depending on the brand&type you can make your own oversized remote controls by any of several methods. Oversized push-buttons come to mind.
Tell us more about your intentions and your son's motor-skills capabilities and I'm sure people here will have suggestions.
