Isn't it amazing what our children will find to be worried about. Has he said "why" this bothers him?
I have a DD(16) who has anxiety disorder. She is always worried about the
wierdest things. I have learned to give her staight answers but never go into to many details. I would never, ever tell her why they need to scan your shoes. She would NEVER get on another plane!
I am a true believer that your kids will take there clues from you. I never ever show that I am nervious in anyway.
On the morning of the flight I would tell him we are going to check in, go thru security and then get on our plane. Tell him how excited you are to get on the plane because that is going to take you to WDW.
I would make sure you arrive in plenty of time to get throught security without being rushed. Also giving yourself enough time to get a treat (if needed) and to calmy get to your gate on the other side. For my DD stress makes her worse... everything has to be calm on flight day.
If you have another adult with you; one adult should be incharge of keeping your son "calm" and destracted. My DH is not good with this, so I always deal with my DD and her isssues, while he deals with
everything else.
Make sure that his shoes are slip-ons or flip-flops. This make the taking them off and putting on as quick as possible. My kids always fly in
crocs...easy on & off.
*If it was me: I would not talk to much about the whole 'security' issue. But turn it into a possitive thing. Maybe, as you reach 'security' if he look uncomfortable in anyway...you could destract him from what is going on. Point out other thing: someones toy, look to see if anyone around you has a dog in there bag (great distraction), count the kids in line, look for certain colors,
anything you can do to keep his mind off of the process. I would also at the moment talk about what you are going to do when you get to the other side...maybe buy a candy bar for the plane ride or look for a snack for the flight.
You guys will be fine... once he goes through the process and see that it is not a scarey thing.