mahhhty, you are divorced right? I have been in and out on your situation.
I think we are in the same boat. I have a b-day coming up this weekend. Here is what I am doing. I am taking my kids camping, they love it and this is what he wanted to do. I am not inviting the XW.
We used to have a joint birthday party as my boy's b-days are within a month of each other; we would invite both sides of the family and friends and have a big to do. When we first divorced I think she assumed we would be friends and still do the joint part etc.
My opinion is when she decided to pursue the OM and want the D, she lost any chance of me wanting to "act" like a family with her, no more of me serving her cake.
I am now dark when it comes to interactions with my XW.
When it comes to the b-day, she will not be invited to any of the festivities I have planned. She is not welcome to the life I am leading now. She decided that when she wanted the D.
In other words, I would not tell her your plans or invite her to anything. You are divorced and she has no right to your family.
It may sound harsh, but that is how I feel. She will not get any more cake from me, literal or figurative.
M:34 XW:34 Together: 10y Living: 9y Married: 7y Son:6 Son:4 Separated: 12/28/13 Piecing: 5/2/14 Separated 2nd: 10/16/14 W filed, but pulled it: 11/5/14 papers served: 1/27/15 D final: 3/6/15