It is kind of silly that you can't tell Zevlor that there are a bunch of kids running a stupid thieves guild that is likely going to get them killed in Baldur's Gate.
I'm sure everyone knows exactly what is going on. Letting them perform petty thievery and have a 'secret fort' is actually one of the safest ways to keep the more adventurous kids from running off and getting themselves in trouble. Like say running into a group of harpies. Or leading some goblins straight to the camp.
If you go in the fort, there really isn't much 'loot' in there. It is more like a 'cops and robbers' kids game than a criminal empire. I fear that Mol and crew are going to get in over their heads when they get to Baldur's Gate, and we may have to save them. Zhent and the Guild don't like people misbehaving in their territory.