you wont have any troubles taking it in a case that is checked , have traveled with our sons as checked.
Call TSA, and inform them that your child has ASD they can then give you the information you need. I find that it differs from person to person and airport to airport.
A few airports have the Autism wings program, not sure if its in your area and when the next one will be.. but it worth checking it out.
Go to your airline booking and request an escort through TSA , you may need to call the airline to do it . you will have someone escort you from the ticket counter to the gate.. you will still have to do all the TSA check points but having that escort makes life just a little bit easier.
also on the TSA website you can print of their card which you can fill out and hand to the agent , you can say what a diagnosis is, what equipment you are bringing and not have to say a word..
You can also request a private screening if they need a pat down.
There are a number of sites that you can go to , to download free Medical equipment bag tags..
we just recently flew and some airlines are now requesting that you take food out of your bags as you go through TSA.
Get your son to watch
YouTube Videos on what goes on when going through TSA, it may help with some anxiety . also write him a social story on what will happen when at an airport and while in the air ..