I’ve done some playing around with ESP32, arduino board, WLED lights and I’m pretty OK with soldering but still went ahead with one of these kits for the reasons you oulined. These look like something I can do with my 6yo son that are a more plug and play than a “from scratch” sort of build.
I would anticipate that 3D Models are going to be designed to hold the standard components with concessions for wiring etc will should make everything easier for him to put together.
As far as price goes, I’ve found that it’s very easy to spent $$ buying the wrong bits for projects or be frustrated when the bits don’t work together. For me personally, paying a bit more for an ecosystem of bits that are designed to work together (along with the forthcoming 3d models) is worth it.