I don't think you will get a whole lot of information when you call. Disney will most likely tell you to check in with Guest Relations when you arrive. You can do so at either park. Tell them your needs and they will issue you a Guest Assistance Card with the appropriate stamp. The stamp will tell the CMs at each attraction how to assist you. Since the stamps vary from person to person, it would be difficult to tell you exactly how it will work. But I have visited with many different kinds of special needs and found Disney to be very helpful with working with kids with different needs. Have fun!
P.S. Have you checked out the disabilities forum? Here is the link, they have a great sticky with lots of information.
http://www.disboards.com/forumdisplay.php?f=20