Hey, 3 days is honestly too short for that long a trip if you want to enjoy it. Driving half a day everyday will you be in a condition to enjoy any stops? My advice is to add more days.
Opt for airbnb on the way for rest..they have kitchen also to prepare food or liquod for the 5yr old..also have laundry just in case the child needs a fresh clothing..check amenities before hand and reviews also