If you have time you could write it up in advance and publish it on the 15th. I say this because I think your post is more likely to be read by more people if you are able to publish it coinciding with the event. That way you can also share the link with anyone IRL that you meet at the ceremony who asks you for more details about it, and in turn it is more likely that some of said people share your post on social media, leading to even more people reading your post.