Longer simply means more than a daysail. The idea is that we spend most the time enjoying what Lake Macquarie has to offer, but make our way up to Port Stephens or down to Pittwater for a couple of days at a time. Much as I would like to take the kids for longer and more adventurous sails, I don't see it happening in the short-to-medium term future.
I don't think I'm going to afford a boat that would fit our family comfortably for much longer that that. At least, not before the kids are too old/independent to spend a week cooped up with each other and not drive me mental
I am pretty sure we're going for something 30' or just over for the very reasons you mention. Our financial limitations don't allow for a good boat much over that size and our family size doesn't allow for anything below it.