I introduced my sweet little guy to Carcassone when he was 3 and a half. This was before I knew there was a Carcassonne jr.
He was really intrigued when he saw me playing it with some other boardgamers.
1) We merely play modified placement rules. When you feel like grabbing a road, then just grab the road when placing the piece. We dont grab each others roads cities etc. Since its not point-centric then he will usually leave his meeps on indefinitely.
2) The secret to the charm that entices such a young pup is simply the pattern matching: roads map to roads, fields map to fields, cities to cities. They catch on very quickly. He is very creative with the game.
3) We examine eachothers pieces. I encourage him to put the piece down where every he wants. He knows it should go in certain place and rotates a piece with my verbal help. He learned a new big people word: Rotate
The game is great for bonding exploring and being creative.