Very rarely have we celebrated our anniversary on our anniversary date. My wife is a teacher and she's usually busy getting the school year started on the date. Before that it was our kid's social or school schedule that had us celebrating a day or week or two earlier or later than our anniversary date. Our next anniversary will be our 30th. I can tell you right now our big celebration will not be on its date.
We celebrate the occasion, not necessarily on the date of the occasion. Even valentines day.
IMHO, if your really think about it, your husband setting up a session to work on your marriage On your anniversary is a hell of a nice way to celebrate your 20 years. It will be fun to talk about on your 25th!