I'd say to have everything packed and ready to load in the morning, and get the truck to arrive as early as possible so it can be loaded.

If possible put all boxes in garage the day before so you can clean the house (or arrange with the new owners if they are not moving in on the same day to have professional cleaners come the day after).

I spouse it also matters on what the other two families are doing... moving into yours... and out of your new one...