I acquired one of these buttons with a built-in LED. This page describes well why debouncing is necessary and provides a possible circuit about 2/3 of the way down. I implemented it according to the below schematic. The time for this debouncing circuit to discharge is directly proportional to the (external) resistance and the capacitance. So I chose the largest capacitor in my box of parts: 100 pF, and I chose an (external) resistor value less than the 20 K internal pull-up resistor but still large: 10 K. These values worked well, so I kept them.
I connected the LED using the below schematic with a 220 ohm current limiting resistor as recommended by adafruit.