I genuinely don't know if IABU here. I will foreshadow this by saying I am under an immense amount of stress.
Context: STBXH has been nothing short of emotionally/psychologically abusive over the last year or so to enable him to save his own face/reputation at any cost. We are separating - he is moving out in May - after I discovered at the very least an emotional affair. I have recently found absolutely condemning evidence that he is planning on moving on with OW as soon as he has moved out despite his continued denials. I can't have him leave earlier due to childcare reasons. He's currently trying to squirrel money away. I'm beyond devastated at the loss of the plan I had for my life, having to share our kids, the betrayal etc. We have two young DC, one with SEN. I am very upset/ angry on a daily basis atm and have no outlet. I also have very important exams coming up; a role that was going to be nice to have is now going to be an absolute must have to keep myself and kids afloat.
On my side of the family I have my parents. DM is very hot headed but has mellowed slightly. Her/DF and my paternal grandparents have spent more time not speaking over the last 35 years than speaking. My DB also fell out with DM and hasn't spoken to her for the last 3 years. He's had more DC in this time so DM is now very aware she has missed out. They reconnected with my DGP last summer and then had a chance encounter with my DB a few weeks ago and now are playing happy families. DB and DGP have always been in contact.
DM is hounding me every time we speak to meet up with everybody and let bygones be bygones etc. I personally don't have an issue with DGP or DB however I do have a very big issue with the way they come and go. My DC have no idea their world is going to be shattered this year. My gut feeling is to stay away so that they don't lose more relationships in their lives when the inevitable happens.
Tonight DM called me to tell me that she is inviting everybody to my DF's birthday party in a few weeks so I'm expected to be there, despite repeatedly telling them that I do not want to introduce my DC to anybody that they might become attached to and then lose that connection with on top of everything that's about to hit the fan. I was really angry at DM on the phone because I have been very clear since they reconnected that I didn't want to be part of it, at least until I was absolutely sure issues had been resolved but now I've been backed into a corner where I don't have a choice. I feel incredibly manipulated using his birthday to get her own way. We always have a tea party, it's on a school night so there's no way to go early, they won't have us a different night because 'it's not his birthday'. She knows my DC love birthdays and have been counting down with my DF to his so I don't know if my anger is clouding my judgement here but I am absolutely furious.
YABU - DM is right, you should see family.
YANBU - You are right protecting your kids from an inevitable mess.