We just returned from our trip to WDW with our two HFA kids, DS4 & DD7.
For the plane rides, we brought Game Boys/DS (2-3 new games), DVD player (with new movies they have never seen), DH's laptop with PC games, markers, paper, magazines (Nickelodeon), special snacks, blankies, small toys, WaterWow tablets, etc. We also were able to declare our DD7's lemonade in small bottles (2) and we brought backup Countrytime powdered drink mix which we used to refill. We did prepare for TSA throwing out our bottles, but they didn't. We had a doctor's note & had our Maclaren Major Special Needs Push Chair/Stroller.
Are you only worried about the airport? I was "puffed" one time (2005) because DD7 walked back through the detector, and TSA requires that someone be puffed after that, so I volunteered since it would have totally freaked out DD7 and the TSA person agreed that it was okay to substitute me.
Does your DS6 get around with no problem? Our DD7 tends to bolt or wander, so having the stroller was very helpful. She also felt very safe there at the airports and in the parks. We were able to see a lot more of the parks because of the stroller and the fact that she could just sit and wait/play her DS before a parade started. I was able to roll it onto the ferries & monorail, but I had to fold it up for the buses.
We had a 5.5 hour flight to MCO, and 2 flights home, with a 4-hour layover in DEN. DD7 was pretty upset during that final flight...she was tired, bored with everything, and wanting to get home. She cried a lot, and there wasn't a lot we could do to console her. I'll search for a better connecting flight next time.
Have a great time!