I myself have not done this but my engagement ring is being made from my fiancee's mother's diamond from her wedding ring (she passed away when he was 12) and his step mother's 6 carat sapphire ring (a family heirloom passed down several generations).. It is taking a while as the sapphire is being cut and they are trying to fit everything together. I think that what you are doing sounds like a wonderful idea. Just make sure that you go to a quality jeweler.