In my opinion, the best way to start development of young people starts when they are toddlers. They should engage with other children in childhood education programs that they like, that challenge them but do not chastise them for less than perfect performance. In other words, activities that aid development of motor skills, social skills and physical coordination. Nothing does these things better than the old standard of coloring.
Once the child is old enough to be learning to read the most important thing that can be done is to encourage, in any positive way possible, the habit of reading.