You mean it's not a real conundrum, with a real conundrum answer. Well you can tell this lot in the office, I'm not - they've been working on it all day, including diagrams, sketches the lot !!
Back to the farmer, fox, goose and grain. On second thoughts I could not sleep till I figured ut out again.
The farmer must row the boat and can only carry ONE other item. So he must row across with the goose and leave the fox with the grain, come back to the original side and take the fox across, but can not leave it with the goose, so he ferries the goose back, picks up the grain and takes the grain to the other side and leaves it with the fox, then comes back and picks up the goose and takes it across. Now all three items and the farmer are on the other side.
Another solution is take the goose, return for the grain, leave the grain and take the goose back to the original side, pick up the fox take it across and leave it with the grain then return for the goose.
Anyway, if the farmer had any sense he would shoot the fox in the first place. "Now as I was going to St Ives, I met a man with seven wives,......................."
As you don't have a boat yet, maybe it will come with a big enough dinghy?
Otherwise: Leave the kids (asleep) locked in the car, while you and the wife take the things out to the boat. Leave the wife on board stowing things and heating the boat up, while you go back to fetch the kids (don't forget to re-lock the car).
I have certainly known other people in similar circumstances who keep their boats on mooring for cheapness, but always motor into the local marina at the start and end of a sail.
So: you get dropped off to row out to the boat (in the wind and rain), while the wife drives into the nearby marina (maybe doing some food shopping on the way). You motor into the marina, to be greeted by the wife on the pontoon ready to take your mooring lines.