Hi Chris, nice post, inspirational. My family visited Illinois this weekend, and it was my niece's first road trip! She recently turned three and could use another birthday memory, so we visited the local CU community fab lab and accessed their laser printer. They have great staff over there to help out with finer details of interfacing with the print machine. It was really easy to finish the print almost immediately after the lines were drawn:

My dad was right about his estimate that ten pieces would be good for a three year old, and here's what she came up with on her first attempt:

That's one fun thing about about Truchet tiles without colors: you can put them in whatever order you want, and you still get a valid pattern. There's no need to judge right and wrong. If the child decides to paint the tiles, especially with more than two colors, then the puzzle could become more difficult to complete. But if it has a lot of colors, then it will have a different appeal to the practitioner.

One comment about your post. Perhaps more could be said about different choices for the boundary markings. There doesn't seem to be an intrinsic best choice, so in this one case, we just chose something that seemed well balanced.

Thanks again!