Hi S.
The gogo Kidz looks interesting. As long as it fits your car seat and it is not kept attached at any time the seat is being used as a safety seat (car or aircraft), it seems to be a benefit to you. Your child should be snugly restrained by the harness at all times while using this device!
For two reasons, I do not recommend checking your car seat at the airport. First, you know how baggage is handled -- invisible damage to the seat could mean a life-threatening injury later on. Second, your child should be IN the car seat while in the aircraft. Too bad if the seat in the front gets kicked. Kids do that without a car seat, too. As a parent, the safety of your child must be the number one concern.
I have concerns about the CARES system. Even on their web site, the photo shows a child with the lap belt worn across the stomach, rather than properly positioned low, touching the thighs. A seat belt worn high (even on adults) may cause severe abdominal injuries. It must be kept low, on the hip bone (This is the main reason for booster seat usage in cars).
For more information, see:
http://www.carseat.org/Legal/FAA_Childproof.pdf
Enjoy your trip!
-- M. Cohen
Certified Child Passenger Safety Technician-Instructor I-575114