Your clients do need to know what is the local government's decision about their ships and their cargo that was held until further investigation, but they prefer to get this information without causing too much trouble.
You are told that they might have a meeting in the Jerralth Castle, and this can happen within the next few days.
You stalk around the castle and find out about a maid that comes out every day to buy some supply for the castle, and the next time you walk to her and start to chat with her, and catch her attention and later, her affection, and maybe with a bit of loosening your purse string, you can persuade her to let you in the servant quarters of the castle.
Then you start talk to the servants as the *friend* of that maid and innocently ask them if there is any meeting in the next few days, and finally get your answer from the butler.
Then you ask the butler if the castle was new or old and hear that it is old but has some new parts, and ask him if he knew who made the new part, and we would say Kratz who resided in the urban part of the town.
You return to town and ask around until you find Kratz's house, and go to a nearby pub and wait till after midnight, then return to the house, unlock a window, and enter through it, and look around until you find a map of the castle, and get out to return to your base.
The next day you meet again with the maid and ask her to let you in in the day of the meeting, go spend your time practicing your sneaking skills and saving money to buy a a few trinkets to help you do the stealth job, and in the d-day, you meet with the maid again and enter the castle via servants quarter.
You look around the quarter, and wait until no one notices you and exit to the back yard, and find another window, and throw up your rope ladder and hook, to climb to the window, and open it to enter the second floor into a narrow passage-way, and gradually sneak your way toward the conference room, avoiding the servants and guards, and maybe knock down a few of them and hiding them in adjacent rooms, and enter that room, and then go into the closet in that room and hide and wait for the meeting to take place.
After the meeting, you wait until the attending people go away and carefully exit the room, and find out that the castle is on guard, because the knocked down guards are found, so you run to the nearest window, open it and use the rope ladder to go to the roof, and run toward the nearest castle wall and use a potion to enhance your jump power and jump from the roof pf the castle to over the wall, and jump down and return to your clients with the new information.
OK, this was pure imagination, but a nice one.