A couple of things:
On the plane, will he be sitting on your lap, or did you get him his own ticket? If he is sitting on your lap, check the carseat with your other luggage and bring an umbrella stroller or baby bjorn for him in the layovers.
If he has his own seat, you can bring the carseat on and he can sit in that in his seat. I've seen people in the airport with the carseats on luggage carriers - pushng around like a stroller.
As far as car seat recommendations - he needs a seat which can be rear facing. In Texas, by law, they need to be rear facing until 12 months, but our doctor says keep them rear facing even longer... I got the Britax Roundabout for my son, which I LOVED off of Amazon for @ $150. It maxes out at @ 65 pounds.
I've traveled with my babies and they are really good little travelers. They LOVE the airport - so many things to look at! We have had a couple of hairy moments stuck on runways with screaming babies, but, as the flight attendant consoled us - "Dont worry - you will never see these people again anyway..."
Have fun!