Just a big bunch of thanks!

The disboards are very helpful ! (disboards.com) I got alot of info there. I also had the book Birnbaum's Official Guide to Disney and that had alot of info in it. I also reccomend the photo pass. They scan your card everytime you get your picture taken at all the parks and send it to an online account. At the end of your trip or even when you get home you can order pics or buy the cd with all the pictures for $99. (I bought the cd and the pictures are excellent quality and high resolution. You can have up to 300 pictures on one cd for that price) Its nice cause you can get pics with the whole family included. They do photopass for most of your character pictures and they are set up all over the parks. (like the castle, tree of life etc) Have fun!

Simon will have a wonderful time! WDW can be a fabulous place for kids with autism if they are allowed to enjoy it their own way.
A few tips from someone who's "been there, done that" with our 3yo autistic daughter because we live near the parks:
Go to Guest Services at the first park you visit and get a "Guest Assistance Pass". This will allow you special boarding priviledges, allowing you to skip lines and crowded boarding areas that might cause Simon problems at most rides. The Disney website says that you need a doctor's letter to get this. I've always carried Bridget's evaluation from the psychologist who diagnosed her autism but have never needed to produce it to get the pass.
Second, even when you are in situations where you aren't using the pass, like character greetings, TELL the cast members you are dealing with about Simons diagnosis. Disney does a great job educating their cast members about dealing with kids like him and they will adjust accordingly. For instance, during our last visit we met Pooh and Tigger in Epcot at the UK. When we were first in line I told the cast member running the line about Bridget. He discreetly whispered to the characters before we approached while the previous kids were leaving. They didn't bat an eyelid when Bridget started crawling on the floor around them (we think she was reacting to Tigger being a cat and doing her cat impression) and just went with it. They gave us a few extra moments and the result was a lovely photo and a little girl who wanted to watch nothing but her Tigger Movie DVD for the next ten days.
Disney can be an especially magical place for special kids...hope you all have a magical trip!