hmmm
I didnt view the link yet, lemme tell you what Id do though.
Ok I got it.
lift the car up with a jack or two. Get under the car and further open the "hole" after removing the fuel tank. Remove the fuel pump thingy and youll be able to touch the under-side of the rear seats (center). Drill a hole in the rear seat from the underside after youve removed the fuel pump/tank. Widen the diameter of the hole until your 4 year old son can get in. Call the kiddy and tell him to go in and unlock the rear door.
When hes in the car, remove the jacks and open the door.
You now have an unlocked car without (a) key(s) and no fuel-holding capability...!