The six of us (four adults and two boys) had a wonderful time for the two weeks we stayed at Diana and Juan's White Ginger cottage. The boys slept on the pull-out couch.
We especially enjoyed meeting other travelers who were renting units next door. Everyone had a good time!
Interesting note: We originally booked another rental in Hilo, but when that suddenly became unavailable, AirBnB stepped in and found us this excellent alternative. They even paid for the slight increase in cost. It is an AirBnB perk worth noting.