The first couple of years I sent cards then called after that. Their marriage honestly wasn't the best, but they stayed together for 47 years and that is very important. In current society there seems to be a philosoPhy of "moving on" and in listening to the pop psychologists of the day they may be concerned they might make the day more difficult for you. As Someone currently married for 32 years and the mother of 2 grown sons I'd like to suggest something. Call them and keep it on the positive side such as "was thinking of your dad today and the anniversary we..." or any memory that would be special to that child and end with "guess I thought of it since this is our anniversary". Sometimes we have to initiate what we need from others because it doesn't occur to them. Happy anniversary, I wish you many special memories today and always.