We have the gogobabyz wheels for our Marathons and I highly recommend it. It took us from double stroller + 2 carseats strapped on like backpacks (if you lengthen the straps you can just put it on your back) to just the kids in the two carseats wheeling through the airport with us carrying shoulder bags. You can even (fairly safely) take them on escalators!
I have had success not taking the gogobabyz wheels off when putting them in seats on various planes, although you must take them off when putting them in a car (it's not crash tested with the wheels on and when you feel how flimsy it is you will see why). That means spending 2-3 minutes per seat when you get to the rental car and on the return.
We are also big believers that the kids will sleep better in a carseat. Plus having it with you means you always have it on the other end for the rental car.
I did have one horror episode on a CRJ where i got the belt so tight in through the seat that the pilot had to disconnect one side of the seatbelt after I fought it for 20 minutes. Now I learned my lesson: don't pass the seatbelt through the same path you would in the car, pass it around the back of the seat, through the steel bars, but not through the seat.