the night before
I don't remember how much packing we managed to get done the night before we left last year, but I feel like this year we're in pretty good shape. The bread and cookies got made, the car-top carrier is mostly packed, and many things are already crossed off the packing list. Plus I prepped the boys: I showed them, once again, all our camping pictures from years past, and also we kept them up kind of late so they can nap in the car tomorrow—but not too late, so they won't be cranky. I think we hit the sweet spot.
I'm trying for something similar for myself: it's good to be a little tired the day before car camping, because otherwise after a full day of driving it can be hard to get to sleep on that not-always-the-most-comfortable bed setup we have in the tent. Of course, I don't want to fall asleep at the wheel, so...
As well as the bread and cookies I had also hoped to bake oatcakes, but I didn't get around to it; instead I chatted with our houseguest for a while. It's important to be prepared for a big trip, but it's also nice to be relaxed about it.