interesting to grandson
I'm working on a layout plan that will eventually be run by an eight year old. I have to keep reminding myself what was interesting about the train my father bought when I was a child. The first train was a Lionel and the my favorite thing was that the giraffe had his head sticking out of a hole in the roof of the box car. The giraff would duck his head to let the car pass under a bar that was too low. I also liked the ping pong ball that would float in the air over the car and I liked the fact that the track would come up the trestle and pass over itself. Prototypical operation was low on the priority list.
The layout I'm planning won't have giraffes or floating ping pong balls, but I'm still keeping the thought that I should have lots of "action" on the layout. So my first design consideration is that there will be no long cars on the layout. This allows me to put more cars in a train of a given length and use tighter curves.
Tighter curves make it easier to put more activity on the layout. One thing I found is that when laying out parallel tracks that curve, use the same size curve radius for both curves instead of a smaller radius on the inside. This allows the layout to maintain the minimum radius no matter how many parallel tracks there are. Also, this causes the track to be further apart on the curve than on the straight, helping to match the fact that the trains need more clearance on curves. The sharper the curves, the more important is including easements into the curves. An easement is a gradual change of the track from straight to the required curve. This article has templates for easements
Model Railroader Magazine - Model Railroading, Trains, Track Plans - Laying out an easement with Model Railroader templates
You might want to model a European or Brittish train. There are many trains with shorter freight and passenger cars.