Can you connect the led wires directly to the piezo, no connection to the Arduino, and get the led to flash? You can detect that safely, no need for the charge-bleeding resistor.
Or connect the piezo to one side of an opto-isolator and the Arduino to the other?
Those take a good tap directly on the bare disk (the disk you showed has a plastic buzzer shell) to flash a led.
I have amplified a piezo disk with 2 BJ transistors and 4 diodes to detect touch and release.
The piezo leads switch polarity going from press to release. To each lead attach a diode pointing to the lead from ground. To each lead also attach a diode pointing out directly to the Base pin of a BJ transistor. To each transistor Collector connect a wire to 5V (I put a 2.2K resistor in the line but you don't have to.) and then connect the Emitter pin of each transistor to a different Arduino digital pin without any pulldown.
Even very light touch caused the transistor on the 'press' lead to load the wire from the Emitter to the pin with a charge that took the pin HIGH. I used a digital read loop to count how many reads it took to empty the charge down to LOW and that was my piezo tap strength analog. Letting up on the disk made the same thing happen on the other pin, giving me press and release data.
That circuit worked without breaking even when I smacked the piezo disk hard with the butt of a screwdriver handle, and I am a big guy with Popeye forearms. I literally tested two 13mm piezo disks to destruction and still no damage to diodes or transistors or the Uno.
There is another direction you may try, capacitive sensing. You will probably have to spend a good bit of time tuning the sensor. IIRC higher values for R need hand close to register at all and the numbers jump on touch of paper over foil for me. You would have to line the inside of the front of the pad with a conductive surface such as foil.
It's tricky but when it works it works.
You could try using an electret microphone and amplifier to let the Arduino hear the sound of the strike. Problem is that a yell would also trigger the mic.
The thin conductive foam between foil sandwich may be your best bet. Any hit would make a short between the foil layers.