No problem for speakers or amps. Speakers have high sensitivity, high power drivers, and the amp only needs a few watts to exceed 100dB. The first thing to break will be your ears, so start at low volume. Increase slowly and wisely.
Lowest note on guitar is E2 = 82Hz, so woofers definitely in play. If he slaps or plucks strings you will get thumps even lower freq and louder than normal strummin.
EDIT: Since it's open baffle with passive crossover that means the drivers have high Q, which is caused by loose suspension and weak motor. So pushing them super hard is not advised.