Had to look up TEHO but otherwise you make some very good points. I'm leaning towards a simple double track display loop with me sitting in the middle. This will offer no great operational potential but will serve to show Billy and his Dad what can be done with a little more than set track. Throw in a little scenery - I love doing scenery - use O-72 and O-80 corners to run the big stuff if needed/wanted - design it so I can easily transport it and I'm in business. I might even consider using Lionel's modular system.
Thanks to all again,
Dan