Jdevleerjr, I took a look at the plans for the switching layout you are planning to build, and one thought came to my mind... I think your son would have far more fun with the temporary but simple layout you have set up.
Why not consider making some sort of small portable layout that could be stored under his bed - if space is a consideration - with the same sort of simple set up. Adults and kids have different ideas of fun when it comes to running trains. A simple layout base with the track, so he can arrange buildings, scenery and such to his own liking.
Just a thought. Just as I can understand the appeal of the switching layout for you, I can also see the appeal of this "temporary" layout for your boy.
One thing I have noticed over the years of being back in the hobby... many years ago, when a dad got his son a train set and built a layout, it was for the son... but dad got to play once in a while too. Today it's reversed... it seems in many cases, that the train layout is set up for dad, and the son gets to play once in a while.
Why not have both layouts? I'm sure your boy would like to help dad work and play on his layout, just as much as he will enjoy knowing he has his own layout, that is really his own.