If his family had a driver, I think it likely the driver picked him up. He hadn't been sick but had been injured doing something awesome that musta impressed his young classmates so I think the little guy wouldn't want Mommy picking him up but of course, we don't know. I bet one of his classmates knows.
JMO
I think JW was SS' driver, not the family driver. PS' school gets out at 3:30 on Wednesdays. Not sure if he was at school that day or not - seems to be conflicting info out there. The school is only a few blocks from the house (much closer than the VP's house!) so he could have walked or his mom could have quickly picked him up. Neither poses a problem with the timeline if LE thinks the crime commenced around 3. Perp(s) could have tied up Mrs. F, then AS and PS when they arrived home and finally SS.