Recently we noticed some new LEGO Juniors sets at the shops. LEGO Juniors is aimed at 4-7 year olds and while they contain the same sized bricks as regular LEGO and include the same basic bricks, they are a little easier and have more pre-built pieces making them quick and simple to build. Perfect for Mr “I want to build it myself”.
Lego Juniors is fine for 3-year-olds who know not to put toys in their mouths. My son, when he was three, was playing with regular System Lego (of which Juniors is a subset) and it was okay. If it's important to you that your son have things like vehicles, or minifigs, and that he build the whole set himself, then Juniors is the way to go.
As I sat back and watched him follow instructions and fit pieces together, I was struck not only by the fact that he was building the LEGO Juniors set all on his own, but he was also ‘reading’.
Right now these skills helped him work through the instructions and build the entire LEGO Junior set all on his own. In a year or two, those same skills will help him discover the magic of reading books all on his own too.