A couple ideas:
-My husband had a work associate who took a cat in, who then proceeded to scratch on her furniture. Someone told her to tape inflated balloons to the area where the cat scratched. One loud "Pop!" and kitty stopped that behavior.
-My daughter worked for a grooming salon (in a popular pet supply store), and they routinely applied claw caps to cat claws. As long as applied correctly, they stay on. Apparantly the cats don't mind them, but I don't know the "ins and outs" of whether the claws retract, or not - I am pretty sure the company would not be able to market them if they inhibited the natural claw movement. But, ask your vet, or your groomer about the details.
-We have a very tall and inviting cat tree. This is placed by the doorwall where the cats can look outside. It also has a tall, jute-covered post that they love to scratch on. I have replaced the jute about four times. But, catnip spray makes it even more attractive.
No, I would not declaw. This can cause all sorts of problems, which you may not be able to rectify.