My Aspie boy (and his little sister, who is borderline, but not diagnosed at this point) are "seekers", not avoiders. They seem pretty opposite of your DS. While they don't like being startled, either (my 12 y.o. is still afraid of the Haunted Mansion!) they tend towards things that will make them dizzy and "lose their stomach". Whether it be the tea cups really fast, or a teeter-totter very fast, or simply spinning in place at home, they love it and seek it out. Though, I know some seekers seek out softer sensations (tickles, feathers, etc.) Mine have wanted to do the "big" rides at WDW/DLR before they were even tall enough for it. Last time we went, DD was only 3.5 and Star Tours was her favorite ride. This year, at just five, it was Space Mountain and Thunder Mountain.
I'd start with some tamer rides, maybe even starting at tamer parks, like EPCOT or AK or MGM. Then let him guide you. I agree with the others about the books and videos and
youtube.
Also, make sure you have whatever comfort item your DS has with you at all times. One of the big things about Aspies, I've found, is the unpredictability of their responses and things they've done a hundred times can all of a sudden freak them out. For DS, it's his Pooh bear, for DD it's simply a receiving blanket (not a particular one, just one.) DS now has a stress rock that he rubs, and we make sure we have that too.
For us, it was important to build in down time. They do get overwhelmed. A bit of sensory overload. We spend the extra money and do TS as much as possible so we can sit down, relax and be served. We'll sit down and have an afternoon snack and find a spot for the parade, we'll go back to the hotel and nap/rest (and what relaxes DS, video games!) I try to find someplace/some time where he can run and he's not jumbled in crowds.
I particularly watch his "sensory diet" when he's at places like this. I bring gum for him to chew on (it helps center him) and make sure he gets things like crunch apples, chips and ice throughout the day. I make sure he drinks lots of water and stays cool or warm and has snacks/food. Body changes (hunger, cold, hot, dehydrated) really impact him more than others and it "sneaks up" on us if we aren't pro-active, as he doesn't realize it until after it's too late.
I watch his face and body cues. He tends to "pick" if he's anxious, gets snappy if he's overwealmed, etc.
He is very much into routine and predictability, so we try to build it in as much as possible. We tell him what park we're going to the next day, give him a bit of a road map of the day (we'll have breakfast in the room, lunch at Liberty Tree, where you'll see characters, sometime in the afternoon, we'll go back to the hotel and rest/swim, and then in the evening we'll go to EPCOT and eat at the Land and watch Illuminations.) I've learned not to give times, to warn him that we may have to walk past something that he really likes in order to use fast passes later, and give him warnings if we have to deviate from the plan.
They both will typically want to do rides over and over. If we're able, we'll let them do it, but we'll set a limit, such as "one time only" or "we'll have to come back to it.
Also, and this was even more prevalent this last visit than others, he is so black and white with rules that it personally bothers him to see others not following them. Whether it's line jumping, or sitting where they're not supposed to, or parking their stroller outside the designated "stroller parking" area, it upsets him and he'll loudly let everyone know about it. Something to always keep in mind.
Hope you have a great time!
