While I appreciate your well intentioned sentiment...I believe the family is best left alone at the moment. This is a solemn and stressful time for them. I think that we should show them some quiet and dignified respect.
Having lost both my mother and my wife to lung cancer I can assure you that prayers are of little use when it comes to that particular form of cancer. I hate to be cynical and of course I wish them the best....But!!!