Something like Processing or some other easy and intensely audio/visual programming interface would be much better since it's made with that in mind and produces near instant feedback.
We don't expect a summer math program to make math work for kids. At best it "stimulates" in the same way a summer-long Raspberry Pi electronics project does, but it builds no foundations. The education market has way too many of these motivational products and not enough investment in foundations.
But any program that focuses on foundations is over a year from application, and that implies that you have enough credibility to go for over a year without stakeholders demanding very concrete results. I suspect that what many people in this forum want are classes which provides a substantial accumulation of foundations over the years.
If you're going to start with web dev, better to teach teach plain HTML and CSS, and enough JS to make something small happen, then let them run with it and help them customize it. Something like an in-browser alarm clock would be interesting. Show them how to change the font, colors, sound, background image (maybe even a background slideshow), and some animations.
Edit: i appreciate Go because there's not as much boilerplate or setup required as with some languages (unpack the tarball, set $PATH, and I'm off to the races) but even those steps mean we're talking about shells and directory trees.
Otherwise, it's really easy to get lost in boilerplate before you even know what the payoff is.
It's good to show what's possible but it isn't fun and will bore them to death fast because it's very limiting for beginners.
I can think of many ways to spark people's interest in cooking or music, but programming seems a bit harder to me. I never thought about why I love it, let alone why others should.
How would you do that?
Combining programming with music is a cool idea - https://sonic-pi.net/
Go is simple but not really beginner friendly. In my opinion teaching novices should start with Ruby (not Python or Javascript that's so often is the case). Show them how to do simple scripts, later build some games together.
Web-dev stuff like React, Webpack, Node etc should be out of the question, it would be a huge turn off for kids; heck it is that even for adults.
A lot of these programs try the 'hard-sell' of "programming is soooooo much fun and important" on participants and if you're not in it for the hard work and the minutiae of what takes to build a "modern web app", you're just never going get that into coding.
If I was trying to figure out how to actually give kids the opportunity to get interested in coding, well, I'd start off trying to go for an open-ended after-school program, where you can drop in and mess around with computer stuff with access to knowledgeable adults if needed. I'd try to get the adults to propose interesting little projects that might capture the imagination of the kids. I'd try to get donated VPS time, not so we can force the kids to make cookie-cutter web apps but so they can put together their own janky terrible stuff, and if they screw up we just kill the VPS and start over. Personally, I think trying to focus on games too much is also a mistake--either you end up with the Logo turtle (educational but incredibly boring) or you have 9 kids just playing Minecraft while the tenth actually learns to script it.