I don't have any great ideas on how to do it right - I'm in the "don't know what I don't know" phase of electronics. Part of the reason I quit playing with electronics was that I already knew Visual Basic pretty well, and so I could program engaging things quickly while the electronics took a lot of fiddling with no understanding to sometimes get a result.

This has been a handicap in my career where I would by default reach for a Raspberry Pi or a National Instruments RIO in places where an IC or a Arduino would suffice. Stuff like data acquisition units (DAQ) and control systems are prime examples. Maybe by giving those applications first? I can think of several projects my 12-year-old self would have found a use for a DAQ or control system.

Let me toss a few ideas your way.

1. I have found internet sources of information byte-sized, disconnected, and incoherent. When people ask about books, I say that they have the "three C's," Continuity, Coherence and Context. Something about the internet seems to encourage foraging over farming, but that might just reflect my current internet habits.

2. I never ran into a partner to help start and grow the idea.

3. "Packaging" is important. Nothing real happens for free. We all knew this when we bought parts or kits. The internet has its downsides. Long story short, just helping people take time away from it can be beneficial. The lure and benefits have to outweigh the costs. I personally got payback, albeit modest, from every kit built and every bit of learning, sooner or later. The "This is fun" aspect might call for a community of users or a mentor of sorts. I have been tech help for a lot of people over time, and honestly, there's no comparison between phone and text messages (still doing it) and "being there", and that is/was key on the after-school idea. Do what works for you and your young (or old) customers.