My advice as a parent and electrical engineer. Buy kits. Don’t go to electrical engineering. There is nothing interesting there. Only lots of wasted time. Your son is not interested how to calculate resistor’s value in motor control circuit. Your son needs no frustration with failing printed circuit boards. He needs something spectacular what moves (and is visually appealing) and causes light errors to learn from.
My path: Chinese 3 wheel chassis, Arduino and I2C color sensor. Line follower robot to be extended to multiple color sensors. It sounds easy, but it will occupy you with your sine for few weekends. Afterwards you’ll see what part is most interesting for your son. Bigger robot, bigger processor, bigger wheels, more speed, a camera instead of color sensor. Maybe just cool paint.
My path: Chinese 3 wheel chassis, Arduino and I2C color sensor. Line follower robot to be extended to multiple color sensors. It sounds easy, but it will occupy you with your sine for few weekends. Afterwards you’ll see what part is most interesting for your son. Bigger robot, bigger processor, bigger wheels, more speed, a camera instead of color sensor. Maybe just cool paint.
Good luck with your project!