Toy Project for Kindergarten Kids

Hi, I am currently in the middle of a project but I am unable to brainstorm a toy idea and am fairly a beginner to Arduino. I would like some advice and suggestions on an easy toy with educational value for kids of 4-6 years old. Thanks in advance.

Is the purpose of the toy to introduce kids to an Arduino?

OR will the Arduino be completely invisible to them?

If the latter, what do you mean by "educational value"? - what area of education?

...R