You should talk to your son again, and stress the problems declawing can cause if it has not been done yet, and tell them you can talk to your grandson about teaching him to use a scratching post, and not scratching up the furniture! Maybe you can visit some times and bring some "soft paws" on his nails and show your grandson how to do it, and that can be one of his jobs with his new kitty! That and emphasizing to him how important play is for kitties, and how much fun he can have teaching it tricks and stuff!