I have to ask: How do you turn the tiefling kids against you? Never had that happen.
There is a sort of a "reputation" system with the tiefling kids, and you can do a few things to influence it. Letting one of the Aradin's gang hit the kid who stole his locket gives you negative "reputation", as is pocketing the "lucky" ring the scammer kid gives you for the coin trick. Shielding the thief and saving the kid from the harpies, on the other hand, gives you positive "reputation". When you get to Mol for the first time, she will list your good and bad deeds, and that will determine your relationship. More good than bad and she likes you, which will help you get your stolen stuff back without additional fuss; more bad than good and she dislikes you, which will result in her setting the guards on you.