I understand the motivation for asking them (i.e. what we hope to get out of it) and the the fact that they may know something (on account of knowing a lot about hunters) - it's just that it seems like we're relying too much on metaknowledge to know that we should even ask the question.
Maybe we could ask why the church forbids the contract - seeing as they went to all that effort with the Bloody Crow and now he's gone for good - whereas otherwise he'd show up again later to wreck some shit. From there segue into asking about the Dream itself and Gehrman by proxy?
Or swap around the order to Laurence/Willem first and hope that Gehrman gets namedropped (Gehrman has mentioned Laurence's Designs before, but never Laurence in a personal capacity as someone he knew)?
Or maybe I'm overreacting and there doesn't need to be some convoluted justification for asking the question.