I wouldn't have kicked their car to begin with, regardless of whether they clipped me or anything else. Kicking their car puts me in a bad position, for a multitude of reasons. This is when you get their tags and call the police.
After the initial fight, to not assume that they would return with reinforcements or greater firepower than they had been holding originally was real ignorance. This trio is fortunate it was only their cars that got smashed, as opposed to them getting lit up and left for dead. Not trying to be disparaging, but as a guy who has lived in major US cities for 30+ years, rarely do the aggressors not return to make clear they are the dominant pack.
Regarding when the firearm comes out, well this situation is so muddled, I'm going to leave that one alone. We could armchair-quarterback that one for weeks and never agree. I will say, that if multiple people are coming at me with knives and bats, I'm making a tactical retreat, preparing my firearm, and calling police.
Some might say that they wouldn't use a firearm to defend their car. In this case, I'm thinking you are justified to defend the property, as it is your place of business, at least for the moment. The gas station/liquor store, the cars on the property, your tools and any supplies or materials that may have significant value, etc. Generally firearms are used to defend life, not things, I get that, but I'm not the type to stand idle while being victimized by a group of individuals who have clearly indicated that they had premeditated criminal intent, and have already been physically violent and threatening additional violence. But that's a personal choice.