The "child seat" part could easily be rigged to fall either straight down or kept as is and most likely fall into place fairly well, the only issue with falling without modification is if something large get's in and gets stuck between the child seat area and the bottom of the cart. Maybe just remove child seat part and use a hinged board folded over itself? Same general idea, stick/trigger system to drop it and let it unfold itself while falling and keep in your critter.