I've collected the bounty from all three npcs, but I also convinced Santiago to work at the casino, so then the quest giver lady told me to find this other guy and kill him.
after that I tried to pickpocket Santiago(while he was working) and I stole his "Big bottle of caps" and then for some reason I could give the quest give the quest lady bounty again from the job, which made me reacquire the other part of the quest.
I dunno if it affected anything, I just reloaded the save.