If DD's car was left at the place where she was working landscaping, then she likely wasn't the person seen at Skyline School between 8:15am and 8:45am - the mystery person who was seen in the Horman truck. So there must be a third party involved.
We've got TH at Skyline School from 8:15am to 8:45am, and an unknown adult in her truck waiting while she and Kyron toured the science fair.
If DD was at her work and disappeared at about 10:00am and left her car there, and didn't return until about 1:00pm, she had to have been picked up and with someone.
I find the fact that TH and DD were both missing during the same time period too much for coincidence.
I wonder now what those two Starbuck employees testified to? Did they see TH and DD together? Was there a third person? Was Kyron and baby K there too? A lot of questions those two employees might shed some light on.
Dede could have parked her car at the school and sat in the truck while Terri took Kyron in. If they were up to something bad, she could have acted as a lookout (cell phones?). Then they could have left at 8:45, with Terri driving to FM and Dede to work. Terri then could have come back and picked Dede up at work after she went to one or both of the FMs.