I am disabled. It is pretty much a given that if I am going anywhere, my wheelchair is going with me. Otherwise, I pretty much sit in the car. I also will pretty much always take my communication device. I can’t speak without it. You will want to make sure that the things that your special needs child needs is in good working order. Few things are more frustrating than having something break when you are on the road.
If you are going to be flying, you are going to want your airline know that you will be traveling with a special needs child any time that you talk to them.
Take a bag with any medicine that you may need. Have it clearly marked, and you should have no problems getting through.