I worry about bringing my car seat on board. It barely fit in the Southwest flight I recently took, and the 777 seats are even narrower (sigh).
What car seat do you have? Is the base/footprint particularly wide? And are you certain the seats will be narrower? Also, at 22 months, is the seat rear-facing?
According to
seatguru, all United 777 versions have economy seats at least 17 inches wide. We had our daughter in a Britax Frontier which could always fit in a 777 seat. She was of course forward-facing, so there was no issue with the passenger in front being unable to recline their seat, but for a rear-facing seat it might be different.
The catch is that my kid kind of likes (tolerates?) being in the car seat. He hates laps.
We would suggest using a car seat if you possibly can. Our daughter was too heavy for the CARES harness (and doesn’t have any special needs so couldn’t use the larger version), and also found plane seats really uncomfortable. Being very small for her age she was in the Frontier until 13 years old and preferred it way more than the airplane seat. She could read, watch movies, and sleep totally comfortably whereas the few times she was in the airplane seat she always complained she could never get comfortable.
The choice will probably depend a lot on whether you’ll be hiring a car. As
LapLap has said, the case for the CARES harness is probably stronger if you won’t have a car, but if you will then the car seat is probably the much better option. As
GUWonder and
FindAWay have said, a car seat is generally much better anyway; they don’t involve any issues with the passenger behind, and most importantly they’re familiar so kids generally are comfortable and more relaxed in their own seat – and will thus likely sleep better and enjoy the journey more.