Okay, what kind of car seat is it? How are you carrying it through the airport? What kind of stroller is it? Is it easy to fold. Can the stroller hold hte car seat and your 6 year-old walk through the airport or will you have to carry the seat and push a stroller? Is your husband or anyone else going to be able to see you at least to the point of getting your luggage checked?
I have done this twice. Once with a 7 year-old and a 10 month old and once with an 8 year-old and a 21 month old.
I've traveled twice with my son's carseat and it's doable. But when my son was 10 months old, I had a backpack as my carry-on I put over both shoulders until I checked the luggage. I wore my son in front and pulled a suitcase with one hand a pulled a Cosco Scenera car seat in a bag with the other hand.
Once I checked the luggage, I just had the backpack and car seat going through security. Before we got on the plane, I took it out of the bag and carried it in front of me. I was still wearing my son in a carrier. My dd sat in the aisle seat. I put my son in the middle seat until I got the seat installed, then I put him in it. I sat between them because car seats have to be at the window. Once we arrived, I put him back in the carrier, the car seat back in the bag, and we went to the bus. I did not have a stroller. We rented.
On our 2nd trip he was 21 months, I had the car seat I could carry on my back. But the one time I posted about the seat on here, I was told despite the glowing reviews it got on various sites, the car seat isn't good, so I don't mention it on here any more. But there are other ways to carry your seat on your back. I carried my backpack in my hand and pulled our bags with the other. I had a small stroller. However, my dd was old enough to push my son until I got the luggage checked. Your child isn't that old and I would not have given my dd that responsibility at 6.
The stroller was small and we gate checked it. The trickiest part was making sure he did not run off when it had to be folded at security. I actually packed our toiletries in checked luggage so I didn't have to deal with that ziplock bag you have to pull out there. I did this both times. I also wore
crocs so I could just step out of them and back into them. So it was just putting my backpack and shoes onto the belt, dd putting hers on. Taking ds by the hand, folding the stroller and walking through. Always sent my dd through first and had her get on and off the plane first.
We are going again in June and I've got a City mini partly because of how fast it folds. He's still a runner. Also consider the stroller you have and the airline you are flying. Some airlines are no longer gate checking strollers that weigh over 20 lbs.
Since you are taking Magical Express, I'm figuring you are just taking the car seat for the plane ride. Like someone else said, I'd consider a CARES Harness instead of a car seat but not sure if the special needs you mention mean your younger child requires it. Our first trip, my son was too small for a CARES Harness and on our 2nd trip, we were taking a cab to a Sea World hotel so I needed his seat. This time we are getting a CARES harness. Several people on ebay rent them. Especially since you have a double stroller, an alternative could be a good idea.
I hope things go well for you. At 6, I'd let the older child carry his/her own backpack. Children can (as someone else mentioned) keep their shoes on now, but I had several talks with my daughter on what would happen. And be sure to dress everyone to avoid setting off the alarm.