Normally, we recommend users to be 10+ years old. But if you are already experienced with coding, you can help your grandson get started with block-based coding(https://www.petoi.camp/forum/software/web-api-to-control-nyb...) after he builds the robot.

He can also code some simple commands to move servos just with the mobile app: https://docs.petoi.com/mobile-app/controller#customized-comm...

He can even make a Petoi robot sing some melodies: https://docs.petoi.com/applications/melody-creation