If you had one of these in the hold an the heating element did trigger, the lower temp of the baggage would likely mean that the final temp of the coffee would not be high. However, that would lose the 'joke'.
If the can cracked and the heating component leaked, the quicklime would make a real mess but unlikely to damage aircraft. BUT if the chemical leaked from the case and the case was near a cable/junction box, it might do some damage.
My guess is that the joke would be better at some other time!