In this one, I'm trying to show how the handle is a little bit below the top bag, but still highly manageable.
Empty, the stack weighs 15 pounds, which is pretty fucking amazing, because the Zuca itself weighs about 10. Could you get one bag that met carryon limits, carried more and weighed less empty? Duh. But it would not satisfy the other criteria. I don't know if you've ever traveled with small children, but there is this age where you really cannot trust them to not have to be carried, but they are too big for any reasonable stroller and they won't ride in the stroller enough to justify bringing it anyway (also, the stroller would weigh more and have to be gate checked). And life sucks if you have to carry your kid and your luggage through an airport. This way, the Sherpani becomes a backpack, the weekender goes over a shoulder, the Zuca transports a kid with the hello kitty bag flipped around the back of the handle. This is a bag that lets me gloat over how prepared I am for a foreseeable period of excruciating pain.
Also, the Sherpani and the hello kitty will fit beautifully under our seats and the other two will take up little space in the overhead. T. is reliable with his own backpack and his clothes will typically fit into this arrangement (assuming the weather is warm and the trip isn't long, if either is false we'd be checking one or more bags anyway).
The Sherpani has a light colored (and pretty, because, Sherpani) lining, making it easy to see into it. It is crazy light. The backpack straps are reasonable. The shoulder strap is okay and detachable. The water bottle pockets on the side are big enough for my genealogy mug and there are additional bottle pockets inside. There is a padded sleeve internally big enough for my laptop or chromebook or some tablets, as well as other organizational features. The short straps don't appear too bothersome, altho time will tell. The big reason I bought this is it has a back pocket with a zippered bottom (basically just like the pathfinder, altho without the middle snap) that acts as a luggage strap to hold it onto the handle of the Zuca or other rolling luggage. This is an uncommon feature in this size bag, and surprisingly desirable (hey, at least to me. I am very suspicious of those travel bungees. Bungees and me don't get along well). I wish lesportsac had more options with this kind of strap (I've only found one, and I don't like the patterns it is available in. Also, it is wider than I prefer -- I like a narrow tall bag for getting down the aisle). I just hooked the medium weekender on using its handles and I'm not sure how that will work with it packed; we shall see. The backpack straps do unclip at the bottom and tug away if you want.
ETA: If you are going, how is that carry on only? It is 4 bags and I haven't even seen your purse yet. Well, it is for 2+ people, me and my daughter. The plus part is my son usually brings a backpack and the rest of his clothing likely goes into the Zuca or the weekender. So the bag count looks like these 4, plus a backpack, a fanny pack (which fits into the backpack if someone gets persnickety) and a small crossbody purse (which fits into one of these bags if someone gets persnickety). 5-7 for 3 people. My husband fends for himself (altho sometimes using luggage that I have purchased in the past because there is a lot of it).