The first thing to do for a child with psychomotor delay will be ruqyah, since children are more affected by evil intentions. In addition, it will be our duty to help him with learning and studying the Qur'an, especially if he is old enough to attend a school for this learning.
On the material side, syrups based on omega 3, 6 and 9 will be effective for the child. There is also lion's mane, a mushroom highly recommended to stimulate the child.