Justin: yeah, that is a big pack from our pre BPL days, made taller by the fact that I didn't open up the internal divider, so the bottom compartment was only half full. Since my wife took our littlest one home in the middle of the night, I attached that one to mine(even taller 90l pack) for the hike home.
Kevin: yeah, might want to get some practice in solo first.
Also you can do stuff like this were we were only ten minutes from home, so if things aren't going well, you can take them home, if you don't happen to live near the woods you could take a motel room that borders on some public land.
After doing this two years in a row, I think I might be ready to take the oldest on an actual backpack a bit further in with on skis. We also picked a very mild night, 16F in the evening, 20 in the morning, very little wind, since I do worry that kids don't always know to add more clothes or cover their face if they get cold at night, I'd avoid the colder dates with the real young ones.