Teaching your kids how to program early is not a bad idea. You are going to need the right tools to keep their attention. The mBot can help. It is an affordable robot kit that gets your kids familiar with electronics, programming, and robotics. It also comes with mBlock which is a scratch-style coding to program robots.
As you can see in the above video, with the mBot, you can build a wall avoidance or line follower robot. You can control the robot by the remote control provided. Your children will be able to use various Arduino-compatible sensors to improve their robot. The chassis is compatible with LEGO and Makeblock parts. You can find out more about it on Kickstarter.