I just traveled with my son at Christmas when he was 14 months old...and by myself, it certainly was a handful! I can tell you that the workers at the airport will take a bit of 'pity' on the "poor mom who is handling this all by herself"...so use it! :)
Definitely take a stroller. Those airport terminals are long, and you don't want to be carrying your little pack of potatoes for that length of time. I didn't do the umbrella stroller, I just took my regular Graco stroller. I felt that it was better because I could recline it if my son needed to sleep, and had the storage area for the diaper bag. It does fit through the x-ray machine, albeit very tightly. Ask someone back there to help, they'll come around and do it for you.
Snacks: I got through before and after the Christmas Eve terrorism thing with a small package of Juicy Juice...and both airports I traveled through didn't even look at it. I also took biter biscuits, Cheerios, crackers, cookies...whatever I could think of! Have a sippy cup or bottle ready for take off and landing, the change in air pressure will effect your son's ears and make him really uncomfortable. My son had a cold when we left the first time, and he virtually screamed when we were landing (taking off didn't phase him!). On the way back, he was completely fine both times...but I had that sippy of juice ready and waiting for him!
Toys: take into account anything that your son might throw. I was on a commuter plane, one that only has 2 seats across one row and the other side of the plane only has one seat. Very close quarters! I only took a few stuffed animals and manipulatives like that, becuase it was something I could easily grab if he chose to throw it. Things like crayons might actually go everywhere...thus really irritating the person sitting next to you.
Naps: I was counting on the nap too...and I think the excitement of traveling made my son force himself NOT to sleep! It was a 2.5 hour flight as well, and he basically slept about 20 minutes on the way there and 30 minutes on the way back. So be prepared in case he chooses not to sleep. I brought his favorite blanket so I could try to cuddle him up and induce sleep, but the blanket adding to the body heat of being pushed up against me made us both REALLY uncomfortable. Poor kid was covered in sweat when he woke up from the 20 minute power nap!
I hope your travels are great!