I've flown with my kiddos (DD's 7 & 4) since they were 11 & 8 mos. old...here's a breakdown of what to expect at the airport:
-Prior to security, organize yourself and your family: After dropping off your checked bags, but before getting in line for the ID/boarding pass check point, empty pockets, take off heavy jewelry, belts, sweatshirts/jackets and place all of this
(if possible) in your carry-on. Make sure to empty any kiddie cups that you may have brought into the airport and make your 3-1-1 baggie readily available.
*I would also have a discussion with whomever else you're traveling with as to who will be in charge of your son and who will be in charge of the majority of carry-ons. This will help with getting thru TSA with little to very little sweat 
-In the ID/boarding pass check point: everyone should be holding their own boarding passes and ID's for this part
(if you're at all worried about your son tearing it, etc., you can hold it for him and present it to an agent with yours).
Your son does NOT need ID...but, there's a possibility you could get a chatty TSA agent, and he/she may ask him some questions...practice these line of questions with him before your trip:
"What's your name? How old are you? Who's traveling with you today? Do you know where you're going?" If a TSA agent does ask your son any questions, it's better for him to answer first before you chime in.
-In the security line: you can now put away your boarding passes (
keep 'em somewhat handy in your carry-on), and remove your 3-1-1 baggie(s), laptops, and any extra liquid prescribed medication that's exempt from the 3-1-1 rule...STAY TOGETHER as a family. Next, grab some bins for your shoes (
your son gets to keep his on, along with any coat or sweatshirt he may be wearing) and smaller items, while larger items can go directly on the belt. If you have a stroller, make sure all pockets are emptied prior to getting to the ID/boarding pass check point, then fold it (
really should be done prior to getting in line) and place it on the belt.
NO ONE CAN BE HOLDING ANYTHING or have ANYTHING IN THEIR POCKETS while going thru the detectors, including any lovies, toys, keys, loose change, etc..
-Now it's your turn to go thru the detectors: who's ever in charge of your son should walk thru first
(when prompted), while your son stays back with another adult in your party. Once you're thru, the TSA agent will prompt your child to walk thru to you, followed by anyone else from your party (
there's always a chance that TSA could pull an adult from your party to go thru the scanners...if that's the case and there's no other adult to help you with your son, your son should walk thru security first and then yourself).
Next, pick up your belongings from the belt and find an empty bench/chair to reorganize, put on shoes, belts, etc.. Nothing slows up a line more than waiting for someone to do all that stuff while standing at the belt (
with the exception of shoes...no one likes to walk around in their bare feet or socks for too long in the airport).
-You've now made it thru security!: Breathe a heavy sigh of relief, then find your gate, grab some bottled water, snacks, etc. and wait for boarding.
-Boarding process: most ticket agents prefer everyone (
including smaller kids) to hold their own boarding pass. Let your son get seated first, then quickly, but calmly put your carry-on items in the overhead bin (
unless they're small enough to fit under the seat in front of you...a much preferred method for my family).
I hope this helps, although it was a little bit more than you asked for!
Enjoy your trip!!
