As long as your dogs are thoroughly familiar and comfortable in their carriers and have had sufficient opportunity to pee and poo before the flight they should do just fine and sleep through the trip.

Taking them out of the carriers during the flight wouldn't be a good idea. They could have an accident or be somewhat overwhelmed by finding themselves in the midst of so many strangers. We must always remember too that not all passengers are pet lovers.

Flying would probably be a whole lot more enjoyable than a 2 1/2 day car trip and a lot easier on the little guys!