Hi Amy!
As far as the hotel is concerned, you'll need to use your discretion in choosing a hotel that is less stimulating for your child, as some kids are stimulated by different things. Some kids would be fine with a brightly decorated room, but over-stimulated by the boat nearby or the monorail that runs through the resort. Go ahead and check out the resorts
here, as they offer great pictures of the resort areas and rooms. I would suggest that when you book your room, request one in a QUIET area (ie away from the pools and 'main' guest areas as sounds can many times be a trigger).
As far as park accommodations are concerned, stop by
Guest Services and ask for a Guest Assistance Card (GAC). Explain your child's needs, and they'll provide appropriate access for them while at the park. GACs can provide an alternate waiting area (usually quieter and less crowded). We ALWAYS choose seats near an exit, as we never know when we might need to leave (I also speak with a Cast Member about exit procedure as well, as I don't want any surprises). We also travel with child-sized ear muffs (ours are made by baby banz)--they are great for loud noises.
Walt Disney World has always been a great place that provides a magical experience for all!
Have a magical vacation!
Amanda