First of all, even though your son is "non verbal" don't assume he "doesn't understand." Both of my sons are autistic and if I've learned one thing in the past 12 years it is to always presume competence and understanding, even when the child cannot communicate that understanding.
Social stories will help. Make one using lots of pictures of the steps to taking a plane trip. Get photos of airline check in counters/kiosks, luggage scales, escalators, parking lot trams, trains/monorails, the gate area, security checkpoint, the jetway,the inside of a plane, the airplane seats, tray tables, flight attendants, the bathrooms, baggage claim, etc. Make a picture book and read it with him several times a day. Keep it with you on the day of, so you can turn the pages as you reach each part. He will absorb that information and will have familiarity with the process.
If you can, take a trip to the airport and show him the parts that you can see without going through the security checkpoint.
Watch videos on You Tube about air travel. There are a bunch about the process of taking a plane trip.
Buy a highly motivating toy and give it to him as soon as you are able to. If he likes electronics,have them charged and ready to go immediately upon boarding. You can now leave them ON during takeoff. If he watches movies on a tablet, have a few loaded and bring headphones.
Bring a stuffed animal or favorite blanket for security during the flight. Bring favorite snacks or candies that take a long time to eat.
Bring a pad of drawing paper and some crayons. We liked crayola Twistables at that age for airplanes.
2 hours is really nothing. It will probably fly by.
If you think it is necessary, inform the gate crew about your son and see if there is anything they can do to make the process easier. You may get an early boarding pass. One time, I had to let them know that my son was prone to meltdowns but that I would be able to calm him down if that happened so PLEASE do not butt in or kick us off the plane!

They were very understanding and informed the pilot and crew members ahead of time. Thankfully, we avoided a meltdown.