ITA with the others. Definitely put the two year old by the window. I'll keep him entertained. You probably get stay in your seats the whole time anyway, so don't factor in the climbing over the stranger in the aisle that you would on a longer flight.

The CARES harness is good if you don't need to bring the car seat at all. Perhaps there is one at your destination or you'll be using public transportaion.

If you do need a car seat at your destination, be sure to bring it on the plane and use it for the flight. Never check a car seat as luggage and even gate-checking it isn't ideal if you can avoid doing that-do so! Using it on the plane means it gets to your destination in good shape. Your two year old will be more comfortable, see out the window better and no worries about it being busted and thrown around by baggage handlers.

I wouldn't worry about a 6 year old on the aisle, as long as they know to look out for the carts. I also wouldn't worry about a child sitting next to a stranger either. I've had to do this many times since I almost always am the only parent flying. I put my oldest next to the stranger because I need to be able to reach all three children and can't do that if I'm the one on the end. We've never had a problem. In fact, I think most passengers would rather sit next to a child quietly playing a video game than a mom jumping up every three seconds to get something for her kids.