Title says it all really.
Ex has asked to see the DC on his fiancees birthday (next sun) so they can meet her (dont know she exists at the moment) as they plan to get married in September and he "felt it was unreasonable for them to meet her at the wedding, which he expects them to attend"
Now we are away Fri to Mon on a holiday which i booked last year, which ex knows about, so offered to meet either side of hol, however apparently that is not acceptable and if its not when he suggests then they wont meet her nor come to the wedding. I am therefore being selfish, unfair and im only doing it because i want to wreck the wedding because i want him back 
Now im sure its not unreasonable to refuse to cancel a holiday so the DC can spend 2 hours with exs fiancee, however he has managed to make me feel that i am, which is complicated by the fact that i dont want to go and DC meeting the fiancee means me meeting her and spending the time there as eldest DC is in play therapy as he "perceives dad as a danger to him" and therefore wont stay with his dad without me as his safety net, so maybe it is reasonable and i just dont want to do it ... sigh