Is that a good choice to kill bottle street gang?

[66Gramms]

So i play with dishonored and i got a quest from some mom or what... in this quest i have to kill the bottle street gang and for that need to use some poison. but i got a message in my diary if i kill the gang with this poison than i kill other peapoles to, who buy from this gang his elixir. I think it's a bad choice and i want to make good choices. So is there any way to kill them without kill civils? or avoid to kill them but complete the mission?

[cyberwiz97]

For the Granny/Slackjaw confrontation in the Flooded District, all you have to do is just accept her first side job. You don't even have to finish it. However, as mentioned, if you don't actually take care of her "gentlemen callers", you won't get your birthday present. Same with infecting Slackjaw's still.