The motor problems you have mentioned denote delay in the mile stones, so there has to be some neurological problems. So just a psych evaluation would be inadequate to address his concerns. He needs to be seen by a neurologist also and should get a CT scan or MRI of the brain.
Please feel free for your follow up questions.
The problems you are telling with your son may denote dyslexia, which is specific to language and writing. Please read this resource on this link to see if this can be associated with him. We can discuss it our further;
A psychiatric evaluation cannot uncover neurological problems, with certainty. There are specialist called as neuropsychologist (neurologists who have done fellowship or special training in psychology), who may uncover the problems. They, by clinical evaluation, investigations and various tests (sometimes these tests can take 4-5 hours), can ascertain whether it is primary psychological or neurological or combination problem.
Feel free, if you have further queries.
Please tell me your concerns and questions so I can help you further.
I am sending you two links, which you can read later: