Here is another set of modular building blocks that allows your kids to build and program their own robots. Easycube comes with cubes that measure 3.91 cu.in. You get various modules to build walking and other types of robots. According to the makers, you can use your LEGO blocks with these bots.
The kit consists of basic, power, triangular cubes, gears, long rods, and everything you need to get started.