Agreed with other commenters' advice to err towards good documentation. Don't just go for cheap.
Another consideration is community: I think the Adafruit guides (https://learn.adafruit.com/) are really great, especially for folks just starting out / who are more project-focused. Poke through there with your kid and see if anything sparks interest.
Shameless self-promo, if he's into music: I make an Arduino-compatible "synth" electronics kit. It does require soldering (so maybe isn't the best choice just yet) but is a nice step towards making something that looks like a real, finished product. https://www.oskitone.com/product/scout-synth-diy-electronics...
Another consideration is community: I think the Adafruit guides (https://learn.adafruit.com/) are really great, especially for folks just starting out / who are more project-focused. Poke through there with your kid and see if anything sparks interest.
Shameless self-promo, if he's into music: I make an Arduino-compatible "synth" electronics kit. It does require soldering (so maybe isn't the best choice just yet) but is a nice step towards making something that looks like a real, finished product. https://www.oskitone.com/product/scout-synth-diy-electronics...