Astrid sort of endorses the theory that the Dark Brotherhood has "ears and eyes" everywhere, and I feel this is the case with the boy;I've first heard that there was a boy named Aventus who needed help while I was in Riverwood (it was one of the first quests I received), arriving in the town, there were a girl and her mom/nanny talking about the boy... I remember the adult said something like he was doing "bad things/evil/black magic things". When you kill Grelod, some of the kids tell you that "Aventus Did It!" that he said he would kill her and he made it...From what I hear, Aventus was making quite a bang on his crusade to kill Grelod. During the Dark Brotherhood quests, you see that they have pretty good "ears", usually they know exactly how your contract turned out even before you tell about it. So probably, even before you took the quest, they already knew it.And the ritual is sort of "clumsy", I mean, you have to dig a whole skeleton/body. Probably the DB just keep some "hall of dead" workers bribed as they do with guards (many guards go whispering "hail sithis!" around you, after you join)Since Astrid and almost all the brothers/sisters don't have much respect for the traditions, probably they were just ignoring the boy. Thinking it would be a kid thing with a kid payment.Since you did the contract, you either could be a precious asset for the organization (that is not going well) or maybe a dangerous competition. Astrid seens to love to play with the whole "smoke and mirrors" kind of intimidation.How they identified you, probably because one of the kids pinpointed you. Or maybe Astrid was on your tail all along.The Dark Brotherhood is composed almost entirely by minorities; So, they probably have a real easy time "talking to their fellow unhappy minorities" of Skyrim.And (as creepy as this sounds) Babette and Astrid seen to have their way with men. Astrid "hides" even from the DB people that she is married and some people talk about her in a very "hunmm, I missss her" kind of way. So probably she has her way.Pretty long winded response, but this is what I thinkAnd, if you didn't follow the DB, I recommend making a "side" save game and playing their mission. They are the most "exotic" missions on the game. There are some creepy/scary moments, and probably the story has some prety disturbing moments... The whole "Torture Dungeon" part of the DB Lair is probably the most "mature" thing i've ever seen in a mainstream videogame.
