You definitely definitely have to use natural coals. Since you like hookah maybe you could do a personal test (and with friends if you wish) with the different naturals available to your business' cost effectiveness?
Anyway, natural coals are a must!
Oops, you said natural coals, sorry!
I'd recommend coconut coals myself.
But with the automated plan you have perhaps bulk wood coals would be better for business? It's hard to say since coconut coals are expensive (but last a long time) compared to something like lemonwood coals which don't last so long but are much cheaper.