I have no issue with the theory of FD pulling up in the red truck at 69WL.
He may have parked it in front of one of the other houses on WL as if he was a service worker.
It being a red truck, JD may not have paid any attention to it and continued on with her day.
I would think, that FD would have parked the red truck in the street before JD left for school drop off and then drive up behind her, once she returned.
Or, left the red truck parked on the street and then FD hide behind the garage and entered immediately when JD returned.
With the Nanny in possession of the Land Rover, one of the 3 garage stalls would be empty at that point and once FD completed the attack, he could get the truck from the street and park it right into the empty stall.
Several different ways that could have gone down.
It would be the easiest for sure and FD would have only needed to jog one time once leaving JD's Suburban at the park.