Trying to avert disaster

[HoldingAHurricane]

My sons birthday is this weekend. We and my sons Dad are hosting his birthday party on Saturday night and on Sunday going out to lunch with the family. My husband is somewhat dysregulated at the moment. As with many pwBPD, family events almost always stimulate some sort of meltdown. I really want to avoid a big showdown this time. He hasn't said anything about the upcoming birthday which we started to plan a few weeks ago (maybe he forgot? and will certainly claim to have forgotten) and I haven't brought it up since he became dysregulated about a week ago.

I have carried on making plans and preparing though which if I don't bring it up until the last minute will probably earn me some nasty criticism about leaving him out and excluding him etc. My issue is whenever I have tried to include him, he becomes ridiculously difficult and the following day completely unbearable. He has been taking overtime shifts on weekend lately as part of withdrawing from the family and I half hope if I don't bring it up until later in the week he will take another and not be around for it.

I am not sure whether to remind him its happening and carry on planning and preparing or just leave it alone since I am painted black anyway? Are there other choices I have not considered? 

[Suzn]

How will your son feel if his dad isn't at his birthday party?

When you want to ask for some thing from your H, this technique may be helpful to you COMMUNICATION: D.E.A.R.M.A.N. technique

[HoldingAHurricane]

Sorry, I explained that poorly. My husband is my son's step-father. His Dad, my former husband, will be co-hosting the party with me/us? at my home and we (former husband and I) have always done family events like this together for the benefit of our sons. My son (who is turning 14) has a cordial relationship with his step-father and I feel pretty confident in saying that he would not be fussed if he attended or not.

Thank you for the dearman suggestion. I feel really clumsy using the tools right now but I am trying.