Have you attended the open houses that GBC College Vocational Program and Humber CICE hold? This is a great way to meet the program staff and ask questions. I would also speak to the Disability Services Consultants at the colleges. There may be other college programs your son may be able to attend.
Have you looked through the Post Secondary section of the Connectability website? The contact phone numbers for these colleges are listed. There may be other ideas on this site for you to look into.