The original house only had 3 bedrooms, a master and two for the children, and the Dows had all of their children before putting on the addition. This means that the children were sleeping 3 to a bedroom from 1908 until 1914, so it is difficult to place any one child in any of the bedrooms. We can make a few educated guesses, though!
Since this bedroom has a door connecting it to the Master Bedroom, we surmise that it served as the room for the youngest children at any time. Today, however, it reflects a different resident. For the last year of Grace's life, she had a nurse living in the house with her and she used this room. Again, it makes sense, since it has direct access to the Master Bedroom.