This incident in the novel made me SO MAD. It was WAAAY down played in the manga. In the novel it was SO MUCH WORSE. The receptionist freaks out at the top of her lungs, yells very loudly about it, drawing attention of literally EVERYONE IN THE ROOM, and the other receptionists ALSO start freaking out loudly. And when Takumi told her to give his guild card back so he could leave and take the twins to safety, SHE LEGIT REFUSED. And the rest of the adventurers in the room crowded around them and boxed them in, so they weren't able to just leave. Actually, if I remember, when Takumi said he was going to just leave (so he could get out of this dangerous situation and get the twins to safety, some of the adventurers that were crowding him even started calling Takumi selfish and said he was hoarding the information about the labyrinth's location for himself, not even caring about the fact that he had 2 young children with him there that he was just trying to protect. Things only calmed down after the GUILD MASTER HIMSELF came down to find out what the crap was going on.
Think of it as if a doctor, or lawyer, or a bank receptionist, or just someone who deals with personal and sensitive information were to suddenly shout out your private and sensitive information out loud in a very crowded lobby where everyone can hear. And not only that, but to NOT take a hint and realize that they just made a huge blunder but to keep freaking out and clamoring about the information at loud volumes and to not listen to you asking them to FREAKING SHUT UP [COUGH-COUGH] cease and desist. And not just the one employee, but to have all of the other employees join in the fiasco and freak out along with them and making everything WORSE. Not only is that extremely unprofessional and would almost certainly lead to not only the employee/s who were involved getting fired, but also company itself could be SUED for damages! And rightly so, too! It's an extremely dangerous situation for the person whose info just got splendidly~ revealed to the whole world, especially someone with very young and vulnerable children. Just imagine having one of the random onlookers that is watching this fiasco happening immediately whips out their phone, and starts to record it, thinking something like "WOAH~ Something hugely interesting is happening just now! I'mma record this and upload it!! I'll get so many hits with this!".
You can only imagine how DEVASTATING the repercussions could be...especially if there were onlookers who had evil/ill intentions and thought that they could kidnap the twins to either threaten Takumi or just sell them into slavery. That's why that whole incident made me SO FREAKING MAD. Even though Takumi did end up refusing to take any requests from that Bailey Adventurer's Guild because of this, they still just ended up trying to downplay it with apologies and sweep it under the rug. If I were in Takumi's place, I'd be LIVID.... (ꐦ ≖`_´≖)