We did that one year dad was in the Navy drove from Rhode Island to CA. in a VW BUG parents in the front two kids in the back AND a poodle in the back with myself and my brother!! GEEZE I don’t know how my parents did it!!
#540 Try 7 and a dog. Parents and us 5 kids and a dog. Mom held the youngest in her lap and us 4 stacking in the back with Pete the dachshund. Not cross country but a 270 mile moving trip. 1966.