Welcome aboard. Have you read the Divorce Remedy book?
What are the ages of you, wife, and kids? The more information/history of the M, the better we can help.
I, personally, don't encourage celebrating wedding anniversaries when the couple has separated or the bomb has just been dropped.....Or like in your stitch where things have gotten worse, instead of better. She wants to put time and space between you. She needs to taste life without you.
Sometimes, the WAW will ask the LBH about what to do. ( i doubt she will, but IDK.) Some couples will take their children and go eat at a kid-friendly place. But under no circumstances should you plan some romantic evening to wine & dine her.
But if you just HAVE to do something, get a very simple card, nothing mushy, and just sign and mail it. No "I love you" or anything extra. In some cases, saying thanks for the sweet memories is okay......depending in the situation. Some people say "thanks for our children". But IMHO, this mostly adds pressure to the WAW and doesn't cause a positive affect.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!