K.S.
We have traveled with my son a lot since he was 8 weeks old. I never had any identification for him until he was 1 1/2 and we left the country. I actually had to get him a passport. Sometimes my husband is with us when we travel but I have traveled alone as well. It seems a little overwhelming at first, but once you've done it, you realize it isn't so bad. I only travel on American and 9 times out of 10 if I want to pre-board they will let me.(American Eagle lets you pre-board) However, I don't always want to pre-board because my sons hates just sitting on the plane as everyone else is boarding. I use a backpack as a carry-on bag so I don't have to struggle so much with it. Just make sure that you have a lot of things to occupy his time. Also make sure he has something to drink on take-off and landing and you may avoid any ear issues. If your son will let you put things in his ears you can try earplanes...they help so the ears don't hurt with the change of cabin pressure. It is easier to wait for everyone to get off the plane before you try to collect everything and get off.
As a former flight attendant I will give just a little more advice-try to get the bulkhead if possible (it is the first row after first class and you have more legroom and you don't have to walk as far back),don't feel bad asking the flight attendants for anything...most of the time they are willing to help a woman traveling alone with children. Don't feel bad if your child has a meltdown on the plane; just ignore the dirty looks...I swear you would think that these people's kids have never had a meltdown/tantrum before(and I said that to a few passengers during my time flying). If any passengers complain to the flight attendants about your child, the flight attendents tend to have more compassion for you than the whiny, complaining passenger.
Have a wonderful trip!!!