My wife is a paraprofessional in a classroom with lower functioning, nonverbal autistic students, so let me be the first to tell you that you rock! Not an easy thing to handle on a daily basis, but also super rewarding in ways others may never understand...
That being said - I believe the vast majority of people have the ultimate compassion for you, but many just don't know how/what to do. Biggest issue we see with my wife's students is that people want to approach and talk, and use way too many words and speak "baby talk" to them, which is often a trigger for behaviors. Nothing intentional, but autism is not a synonym for stupid.
Universal, in my opinion, has many more triggers than Disney. Their tagline has been "ride the movies", and there is an overproduction of lights, sound, and motion. Disney has many more rides/attractions that are more subdued.
I know Blue Man does a special performance, and many cast members will bless you with extra time and patience to make a Uni vacation special. Only you know the true triggers for your child, and only you know what their true likes as well. There will be a lot of both at Universal.
I wish you the best!