Joey Jr. always had his back pack, what better way to make them look like they just went on a drive, or vacation? If his back pack HAD been at the house, I believe several family members and acquaintances would have said "this isn't right". They noticed the double stroller was still in the house, maybe the back pack would have got them to push the button?
CM had access to the storage AND the property in Victorville. They may have been put there til they were buried.
Joey Jr. may have had the back pack on or one side looped on his arm when he was murdered seems the most likely scenario.
BBM. Was this family property or somewhere he rented?