Just checked actual dimensions on Aquahound for you- a far better buy than that other RC5.3
and with a 2x2 layout much better if you are out with only 1 other especially if a youngster.
I wouldn't be happy with children on a rear bench personally single jockeys every time for me - but don't want this thread diverted onto a seating debate
On the snipe rapide trailer I have tip of ball hitch to end of sponson 6.50m. and its's not really a long drawbar.
Height with an RC A-frame 2.30m. Added to that are Nav light and 0.5m antenna giving total height on trailer 2.80m. You could relocate nav light and antenna or replace with a fold down one, or even ditch the A-frame entirely - although as the kids grow they'll want to be towed on stuff no doubt.
No sure if that helps with the storage issue but might put an RC5.3 - which would fit the bill otherwise into context on dimensions. Give me a shout if you need anything else from me.