Modular design - input much appreciated

where modules join, you should avoid a curved track mating to the next module.  end the track at least 2-3 inches short of the module edge and use small 4-6" straight joining tracks to piece the modules together.  even easier to deal with when you keep all the mating track segments equal length.

Will this be in your home, or at "public" events? If "public", are other people part of your modular setup? BTW, I was part of a modular group for 4 years.

For module construction techniques, suggest you have a look at the guidance available from the various modular groups. No need to reinvent the wheel. Track planning is up to your own imagination. Here are some links to get you started:

http://www.trainweb.org/ttat/ttat_module_spec.pdf

http://www.trainweb.org/Nation...ers/NCTStandards.htm

http://hirailers.org/PDF/Stand...raight%20Modules.pdf

http://hirailers.org/PDF/Stand...0Curve%20Modules.pdf 

http://hirailers.org/technical.htm#Module Building Techniques

Hi Lucky 13, Concluding that you would want the layout to be kid-friendly, may I suggest that you place delicate and the more precious objects away from the edges of the layout, beyond where children can easily reach in or grab things. They will reach and want to touch objects because the appearance and action of the whole composition will be irresistible. Even some adults find model train layouts irresistible to touch while it is operating, and even before it starts moving.

Here are some examples, from my layout, of what I am suggesting you consider...

In this section, the trains themselves  are a barrier, being situated right up front, along the viewing-aisle, since the entire operation is about trains, but the delicate details, such as figures, etc. are located out-of-reach to most children...The viewing-aisle is on the right of these shotsHere is a view of the same aisle and layout section, but as seen from the opposite direction, placing the viewing-aisle on the left of this photo. The bridges (by Stainless Unlimited) are tempting and sturdy, inviting hands to touch them, if desired.

Here is part of another area of my layout.... You can see that the trains are along the outer edge , with the viewing-aisle out-of-frame on the right of this photo, with all the delicate structures and details situated well inside the "acreage," safe from exploring little hands.

FrankM

there is a difference between a layout made to be modular (transportable) and a modular layout (compatibility with other modules).  i believe the OP is attempting to go for the 1st type, though an interesting idea would be to make at least a piece of it both intra- & inter-modular.