Okay, I'm going to throw out an off-the-wall ideas.
1. This inn has a team of Hot Springs genin protecting it, right? Is there some way we can get them into a confrontation with Joutaro and his companions? This is supposed to be sort of a "neutral zone" for ninja, but they're still the local authority. If they come up and demand that Joutaro and his companions submit to questioning then even if he's able to smooth things over, they probably all get dragged out of their rooms for a while.
2. Get access to the room next to Joutaro's bedroom. Drill a hole in the wall in the middle of the night. Use Noburi's water-whip to chakra drain him in his sleep. Do the same with his companions on the other side. (Lace their dinners with a mild sedative that night to penalize Awareness rolls? I know there was a discussion about the difficulty in obtaining it, but still.)
I think we may have to give up on making a smooth switch. It's going to be hard enough to get access once, let alone twice. The best we could do is carry a collection of scrolls and hope that one of them looks close enough to the info to fool casual inspection for a little while, which would be entirely a matter of luck.