IMO JW picked SW up that night because they did not want to chance her waking up and maybe identifying one or more of the killers. I have read all the theories about the killers wearing masks, but if one or more of the W's were present this particular child could identify the killers by their voices. They also would not have wanted to run the risk of a stray bullet hitting her in the melee and if they picked her up and held her to get her out of harms way she certainly would have known by instinct if nothing else it was them.
It is a sad testimony to the ruthlessness of the killers that they had no such concern for BR's waking up. Granted they may not have known BR was there as his being at FR's was a last minute decision on the part of CR.
But then again if CR saw JW that night then he certainly saw her, and may have figured she was dropping off BR. I shudder to think what may have happened to BR if he had awakened and called out a name that was familiar to him.
That the people who planned and/or executed these killings thought it would be "safe" to leave the smaller children in bed with their parents while murdering them is just appalling.
Appalling. No words.