They have made rules regarding Wedding Anniversaries. They want them to be modest and small celebrations if they are going to be celebrated in the first place.
Watchtower 9810/15
Whether they focus on this happy occasion in private, just as a couple, or they have a few relatives or close friends with them would be for them to decide. The occasion should not become a mere excuse for a large social gathering. On this occasion Christians would want to be guided by the principles that apply every day of their lives. So whether one takes note of a wedding anniversary or not is a personal matter