Car seats, strollers, AND baby diaper bags are not considered carry ons. Hopefully you will not try to carry all three. But technically you could, not to mention your own carry on luggage and purse... that would make for a lot. All of the above would be checked at the gate. I would check with the airline on the carseat, some require it over the age of two... and it has to be FAA approved. If you do need to use a carseat you also have to buy another seat. Be mindful of what you carry to gate check, you have to go through security and they make you unpack, stroller, carseat, diaper bag, ect and it all has to go through the metal detectors. Kind of a pain when you are holding a baby in one arm and trying to take your shoes off with the other. We are traveling during the holidays as well, with our 15 month old. Luckily, we are going home and all the necessary will be waiting for us there to use. We go to the airport with as little as possible. If I were you I would consider borrowing or sending one ahead of time, if you can. I also send a box ahead of us with diapers, wipes and anything else I can throw in.