This can be a tough one. I work with autistic preschoolers and know the population pretty well. You want to show something that will keep most of the kids' attention, but you don't want to show something that will scare them or play into any of their rigidities.
For example when my son was 3 (he has high-functioning autism), he wanted to watch Toy Story over and over, all day, every day. We finally had to put the tape away and encourage him to do other things. If you show a movie that a particular family is trying to avoid, they might not want to attend.
Another scenario: My son loved Thomas the Tank Engine, but he absolutely hated the movie Thomas and the Magic Railroad. The characters didn't look or sound right to him because they were different than the TV show. He watched the video once and said "never again!" If movie night was showing it, I would have had to keep him home because he would have tossed a huge fit and ran out the door if it came on.
I have kids in my class who have fears that we don't even know about until we put on a video. We once showed an alphabet video with an alligator for letter "A." One little girl freaked out and ran to the back of the room. We figured out she really does not like alligators, real, cartoon, pictures, etc. So, if a child in your group has a fear of a particular animal, vehicle, or character, you might have a problem.
Since you want movie night to be fun and accessible to everyone, I would suggest a short parent questionnaire. Let them know you will do your best to choose a movie most everyone will like. Ask if their child has any fears you should know about, if there are any movies they really don't like, if there are any movies or themes your family would rather avoid, and finally, what are their favorite movies or characters. This will help you narrow it down so that you can choose something appropriate. You won't be able to please everyone, but it will help you narrow it down to a good choice.