Also call the DayOne Network which used to be called Child & Family Connections of Kane/Kendall Counties. It is on Fabyan Pkwy. just East of Kirk Rd. It is the Early Intervention provider for Kane County. They can hook you up with evaluations, therapies, etc. before your son gets into school.
My daughter (almost 6 years old) has some sensory issues, and it has been tricky getting her what she needs and recognizing what is sensory-related and what is not. Another great resource is Marget Wincent -- she is an OT who I believe is out of Wasco. She is THE person in the area for therapies such as listening music therapies for sensory and attention issues (among others). She is fantastic. Let me know if you need some more assistance or just want to talk. I am happy to do either.