I'm currently playing as a halfling monk who is very fond of a drink. Let's say I encountered some enemies sitting around a campfire. Through means of deception or otherwise I ingratiate myself with the group enough so that they do not consider me an enemy. (My overall plan is to attack them).
At some point I cause some sort of commotion, for example spitting some of my highly flammable drink into the fire causing it to rear up and distract those sitting around it.
I am aware that I was planning this however the enemies weren't. Would I be able to use this distraction as the basis of a surprise attack?
TL:DR Can a planned distraction caused by my PC while enemies are aware of my presence, that sufficiently distracts their attention, constitute basis for a surprise attack?