Are family celebrations like anniversaries allowed on Fridays?

Within reason. If you can pick another day, Thursday or Saturday, that probably would be better. Friday is one of those somber days that we should be keeping somber. That is my opinion, and someone may differ; there is no rule on it. But going along with our tradition and with what Friday is set aside for, and what happened on Friday, that should be our day when we do not have as many celebrations, family or otherwise.