In a word, you.
I don't play Dungeon World myself but just as a general rule, you'd probably want to direct your question at just one person. I think if this 'carpet bombing' is a frequent thing, you'd simply state from the start:
DM: Now, which one of you is most likely to know about this dungeon?
Player 2: Sure, I think my mentor told me about this...
And so on. You could arbitrarily say 'now hold on, only one of you can roll about this place' too if you like or alternatively 'I think it's high time we move on to you guys getting to the dungeon'. As the DM, you can set the pace, which includes skipping over people's rolls. Part of the challenge lies in the mystery and I presume the players would want this too.
I assume you are talking about a hypothetical situation here. I'd expect, most of the time, people roll for situations as they unfold rather than presciently; this is certainly true in my experience. If we change the example to say, disarming a trap, similarly carpet bombing moves wouldn't work because each action would presumably have a component reaction which would change the situation.
One important thing to note though is that in the case of NPCs, they shouldn't just be fonts of knowledge that you can simply read like a book. Whilst sometimes the players may be able to tell you the motivations and information they can glean from NPCs, it should mostly be entirely your discretion as to who these people are. As far as robbing the house of One Arm Owen goes; to my mind, that's kind of going against the spirit of the game. If the player says they really did rob the house of One Arm Owen, then cool but they don't just get to say 'I got away with it, no one caught me and I also got these very useful scraps of information'. Why not play the actual robbery out and see how it went? What information
did they obtain and so on.
The whole discussion is pretty interesting and you might find
this page interesting for more information.