There are some links to past threads about autism that may help you also. The links are on the disABILITIES FAQs thread. Even though your children don't have a diagnosis of autism, many of the ussues and things that are problems are similar.
One other thing to also look at are threads about small children who don't have disabilities. Many toddlers and young children have problems with darkness, noise, sudden things. If small children
without special needs commonly have problems with a certain attraction (Bug's Life, Stitch and Fantasmic come to mind), that will be a good 'flag' to you that your more sensitive child may have issues too.
The
Passporter's Open Mouse book that was mentioned is a very good resource. I was one of the peer reviewers of the original book, which is very similar. I have a couple suggestions when looking at it.
1) It's a very large book and can be overwhelming, so I'd suggest just paging thru it to get an idea of how it is laid out and what sort of information is in it. Then pick a section to read thru; use Post It notes or flags to mark things you want to come back to. Then, re-read those parts and underline or highlight things you think are really important. If you start underlining at the first reading, you may find you have marked so much that nothing stands out any more.
2) Read the whole listing, not just the 'coded' part. In the ride/attraction listings, they have things divided up by codes (a heart for people with heart conditions, for example). I would suggest not looking at the codes - just look at the write up in general. For example, they may have "stairs" listed under "Mobility" or "Heart". If your child is fearful of going up stairs, you may miss that information if you are only looking for 'your' code. Many things are like that; different things about the attraction were assigned to a particular code, but people with other conditions might find that information just as helpful.
3) Some attractions are listed as "Best For" certain conditions or "Worst For" certain conditions. It doesn't say why though and I know that some of the ones that were listed as "Worst" for people with autism have been posted here as the favorites as some of our posters who have autistic members of their family. And, some of the people may have not liked an attraction because of loud noise might have done OK if they had earplugs.
So, I would take those recommendations with a big grain of salt. Look at the description and search out information (like
youtube videos) to help you decide.
I have started an Epcot FAQs thread that has information about many of the Epcot attractions, with pictures of the queue and information about noise, lighting, etc. That might be helpful. I'm not done with it, but it does have information about many of the attractions already.