Only 9 months left so what educational toy can Ben, Karen and Felix come up with for the young and upcoming maker in the family this Xmas ?
Rather than reinvent the wheel then it may just be a case of 3D printing various widgets to interface actuators and sensors with existing toys such as Lego and Fischertechnik so as to allow them to interface better with common Arduino and R-Pi type peripherals in the maker arena.
The Seeedstudio 'Grove' system may be worth considering as it has shields both for Arduino and R-Pi and then a vast array or sensors and actuators which can be easily plugged together without the need for soldering. It is also has a small number of standard mounting footprints which may make it easier to connect to a custom 3D printed 'brick' to interface with the existing Lego / Fishertechnik components.
http://www.seeedstudio.com/wiki/Grove_System
For those not familiar with Fischertechnik fischertechnik GmbH - ROBOTICS
then one advantage of this toy is that you can purchase aluminium extrusion in the same profile as the basic building blocks which allows for much larger and more stable structures. Although as you can see from this video you can build pretty large structures from the standard components.
https://www.youtube.com/watch?v=9xZLyUMSlBE
Perhaps this project could then be extended into a series of STEM-based mini projects providing further educational value.