First of all, I am sorry for your loss.
Personally, I would celebrate her life and the memories you had with her. Specifically, you could go to dinner at her favorite restaurant. Take a friend that knew your mother and you can reminisce the times you all may have shared. You could visit some of her favorite places. If you are a scrap-booker, you could take pictures at her favorite parks and make a page out of them. Only you know what is best for you at such a tough time of year, but try to look at things a little differently than a totally sad day. You will feel better and thinking about happy memories will always make you smile.

I almost lost my mother a few years ago, a week before my wedding. It was a miracle that she was able to make it to the ceremony, but in the week prior, I thought about a lot of things. I know that she would have wanted me to proceed with the wedding for one and she would not want me to mourn over her passing year after year. I talked to her about this and she confirmed my thoughts. Not many people don't think about these things until it is too late. I am grateful that I had this talk with her and I know that I will be very sad when she is no longer walking this Earth, but I will do what I can to celebrate her life after her death.