I bought Lego Mindstorms EV3 while son was 3 years old - just playing, making mechanisms, winter time. He could create something by himself. The hard part was staying simple - waiting while I made even simplest robot was to exhaustive for both of us.
He is 4 years now, stacking (lego classic) is simpler, I enjoy it too. But most complex models he built with Fischertechnik (free exploration). Universal 3 [1] is amazing set (with 40 models book) and connections are much sturdier, blocks bigger, more ways to connect.
Building Lego Technic vehicle requires thinking ahead. Looks like the way forward is extending classic with studded beams (phased out in modern sets) or (from Technic side) building with Beam Frames (64179) [2].
He is 4 years now, stacking (lego classic) is simpler, I enjoy it too. But most complex models he built with Fischertechnik (free exploration). Universal 3 [1] is amazing set (with 40 models book) and connections are much sturdier, blocks bigger, more ways to connect.
Building Lego Technic vehicle requires thinking ahead. Looks like the way forward is extending classic with studded beams (phased out in modern sets) or (from Technic side) building with Beam Frames (64179) [2].
[1] https://www.fischertechnik.de/en/products/playing/advanced/5...
[2] https://rebrickable.com/parts/64179/technic-beam-5-x-7-open-...