I wonder if it would be a bad idea to just ask her. You two seem to be in a place where you can talk like this. How about telling her how conflicted you feel, that you want to mark the occasion but it's obviously not your happiest anniversary. See what she thinks about it?
Adinva 51, S20, S18 M24 total 6/15/11-12/1/12 From IDLY to H moving out 9/15/15-3/7/17 From negotiating SA to final D at age 50 5/8/17-now: New relationship with an old friend __ Happiness is a warm puppy.