The Photoshop script isn't working for me, so I thought I'd list something that isn't quiet as good asquite complete automation but works pretty fast.
Create an action called "Scale 25%": Decrease layer size by 25%. Stop.
Create another action called "Choose next layer": Select one layer down: alt [ ...AND select action "Decrease layer size by 25%" and play. Stop.
There, done! Now, place all layers that you want to decrease by 25% into one group. Choose the top layer.
Run the "Scale by 25%" action one time. Then run the "Choose next layer" action over and over. Just keep pressing the play button on the action and watch the layers shrink around their own anchor point until you're done.
It may not be complete automation, but clicking play1 button over and over is actually really fast. I just did it to hundreds of layers in about 1 minute.