Anniversaries can be very difficult for many betrayed spouses, including myself. There are a number of posts and threads about the topic.
I still get my fWW something small for our anniversary each year and usually take her to a nice dinner.
This past year was our 40th anniversary, so as a surprise I booked us a week in a really nice resort that she has been wanting to visit.
She said she did not deserve it and almost did not want to go because she feels so guilty for everything she did, but we went and had a great time.
It may be true that she does not deserve it. I would never say that to her because it seems unnecessarily mean and she has been trying really hard for the past few years to be an awesome wife and mostly succeeds at that.
Also, I do this partly for myself. I want to be able to look myself in the mirror and know that I am a good husband and did not lose my own ability to live with compassion and integrity just because she did for a time (an unfortunately long time).
I also would not want to embarrass her as it would be extremely noticeable to a lot of people if I ignored our anniversary, especially a 40th. I understand that if she was embarrassed it would be something she brought on herself, but I chose to stay and I fully intend to make the best of it and be the best person and husband I can be.
As far as vow renewals, I do not think I would ever do that, although she has never asked. I do not need to renew my vows because I have always kept mine. Also, it does not seem to me that vows are particularly meaningful to her as a former serial cheater, so it would feel like a meaningless gesture to me. Why would her "vows" mean anything to me when I have seen she does not particularly value them or have a problem repeatedly breaking them? In fact, I think it would probably trigger me and I can see myself spiraling now. I may have some work to do here as far as my feelings on this, but I guess it is actually a moot point at this time for me at least. I do really feel fully reconciled and that I have fully forgiven, but it does not mean some things are not still hard to think about.
Best wishes to you!