I think maybe your reply implied that you would make sure the kids were ready to go when he got there, which clearly wasn't the case. Perhaps it would have been a good idea to tell him that you were fine with it, but he needed to coordinate it with the kids himself.
Yes, AS, this was my preferred mode of dealing with invites out. But my XH will have none of it. He insists that I have to be the one to deal with the kids. He even insists that I must make them go out with him.
I find this aspect especially strange.
And yeah, i take your point about paved and smooth... Despite my best efforts to be getting on with things in a detached way and treating him as a mere acquaintance, the kids' responses to him are often not 'acting as if' everything is fine and OK. I understand why, but it often means that his infrequent visits home are fraught. Not the sort of experience anyone wants, but understandable all the same. The kids are hurt and bewildered by this strange man who used to be their father.
