I would buy a good leather furniture cleaner. With them sitting in it smoking, and all of the smoke, nicotene, and other garbage settled right there on it, you can't just treat it with some smell good stuff, you need to really wash all of the garbage off of it and then retreat the leather.
Look in the phone book for a larger furniture store that sells leather furniture and then go done and talk to them, they prbably sell something. The other idea, again, look in the yellow pages, to find a fire restoration place to see what they recommend. These are the companies that your insurance people will call if you have a fire. They come in to clean the fire damage and clean out all of the fire/smoke smell so they have to clean all of the furniture. If you have a local house insurance agent, call them for who they use.
Bill
Nodwell RN110 out moose hunting. 4-53 Detroit, Clark 5 spd, 40" wide tracks, 10:00x20 tires, 16,000# capacity, 22,000# weight. You know the mud is getting deep when it's coming in the doors.