When your childs grandmothers hate each other what do you do?

Help!! I have made an absolute hash of things! I feel like the piggy in the middle! my sons 5th birthday is tomorrow, I have booked at a childs party venue, my family and my sons fathers family don't get along, there have been some things in the past that make each dislike the other especially between my sons fathers mother and grandmother and my mother, the first time my mother and I met my sons fathers grandmother she insulted my mothers home, and was very rude. there were slight doubts as to my sons paternity and she was very demanding that I get my son dna tested before she would acknowledge him as her great grandson. progress has been made between them and myself however my mother is still disliking her alot. for the purposes of this post I shall referr to my son as TJ, his father as MM, his fathers mother as K and his grandmother as V and my mother as D. well V rang me 2 months ago saying she wanted to surprise her daughter K with plane tickets here so she could see TJ on his birthday at his party. I thought ok shes doing something nice for her daughter I may not like them but I can set my feelings aside for my son, I told D that night when we had our catch-up over the phone. I thought she would be unhappy yes but that if she didnt have to see V and K or be in the same room she would still be ok about coming to TJs party. well she was soo angry and upset she didnt speak to me for over a month, I hoped to perhaps get V and K to do their own thing with TJ to celebrate, when D makes her mind up shes like the proverbial rock, unmovable. D is finaly ok and talking to me, she would only agree to go to the party if V and K wouldnt be there, I spoke to V today and she wasnt happy about not being at TJs main party (I understand from both points of view) and said she couldnt understand what D has against K but the thing is its not just K its V as well D cant stand. so V has decided to celebrate with TJ at his daycare on his actual birthdate (monday) I'm just praying as hard as I can that she doesnt start a dust-up with D or cause trouble because shes feeling hurt and resentfull. I just dont know how I could have handled them better, I'm not a peace keeper or very tactful, I'm blunt even though I try not to deliberately hurt anyone. oh lord let me survive!! any advice on how to keep things peacefull would be appreciated, I'm so stressed!! TJ's dad M hasnt been really around much he blamed me for not bonding with his son and I told him the truth if he isnt around consistantly or when he is he not really playing with his son, well he got mad and made trumped up allegations to CYFS, he is also going to be at my sons daycare when we are doing the pizza for the kids on TJ's actual birth date. its so messed up all I wanted was for those who love my son to be there to celebrate and for my son to be happy.

Quite frankly, it's TJs 5th birthday. It's his day. Organise your party for him and invite everyone. Let them sort out their pettiness and let TJ enjoy his celebration with them or without them. It's their call. It should all about TJ, instead, some very immature and childish adults are making it all about them. Maintain your dignity and sanity and ignore them and just get on with it and ensure TJ has the best birthday any 5 year old can possibly have.