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.
The main thing I got out of teaching myself how to do it from scratch is the discovery that there's possibly nothing more frustrating and less satisfying than spending days and weeks designing and building relatively simple electronics projects from scratch and then discovering all the fascinatingly inscrutable ways your designs can completely fail to work.
This isn't to say that there aren't people who love it. But I'd guess that for every one person who does there are 100 people where immediately diving in at such a low level kills all the joy. Maybe compare it to trying to get a 10-year-old into games development by starting them off on z80 assembly language.
Tangentially, my time learning electronics straddled the demise of Radio Shack, and I think that might be part of what made it less fun than I expected. With Radio Shack, if I realized I needed a component I had a decent chance of being able to acquire it that day, probably for less than $1. Now that sourcing components almost always has to be done by mail order, realizing you're out of that one size capacitor stalls your project for a week or two and might involve being willing to pay $10 shipping and handling for a $0.15 part.
I feel the opposite! I can usually get components next-day on Amazon, and I can get entire circuit boards _assembled_ from China in about a week. Maybe I'm not trying to do anything particularly hard, but I keep being pleasantly surprised when things work on the first or second try
When I was a child, I loved electronics. I would take apart various electronic devices, but as you said, it was just frustration with no feedback. Then my father, seeing this, took a speaker and made a circuit that emitted noises. I loved it.
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!