Just playing around with it with the remote they don’t have to be older than maybe in elementary school like my neighbors kid. If you mean assembly and doing some programming I would think middle school with an adults help for a few steps in assembly. Some of the toughest assembly is getting the wiring to go through to where everything can close properly, otherwise not too bad.

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