So as I turned on my computer I found my screenshot comparison (trying to find the location of where the Christmas bag was) and I got a haunting thought. Forgive me cause this is incredibly morbid to think about.
The roads are dirt but they seem to have lots of plots of land in Cal city. It's still a fairly new area and I suspect development is probably happening, as there are lots of half-done roads, seems they're building the city out. September would have been months ago, but what if they hid them on a plot of land being developed (do they do house foundation and cement there, unfamiliar with California construction)? Maybe the other kids were on vacation to hide the disappearance and they were waiting until the house was built?
Amateur speculation