I think he made the decisions based on his best interests actually, Fayc84. Were they still together do you think?
WRT talking about children, I have to say, one thing that made me almost throw up was a text I saw from my exH to the GF 'Have just read a bedtime story to 'DD4's name' and am now going to sleep but thinking of you.' . It really angered me to see him talking so freely about my DD with this woman, making himself out to be such a 'loving father' to DD4. I also found he had been talking to basically random strangers on dating sites (I read his entries and some e-mails to female prospects) about our children. It still angers me that he would use the children this way and present himself as this sensitive, doting daddy figure some men at least have the decency to buy a cute puppy when they're trying to pick up women.
I think the exH is trying to brush the previous relationship under the carpet by insisting on the happy families thing. It is incredibly hurtful to the mother of the children of the first relationship to have to put up and shut up about what has happened, at breakneck speed and hurry the children into accepting the new reality.
He is actually using the children here to hurt the OP, rubbing her nose in the new relationship by insisting everyone get on board with visits. In effect, he is telling her by insisting on everyone getting used to the new arrangement, that what went before is ancient history and that she needs to embrace the new situation it's like salt in the wound. She will no doubt be expected to field the questions the DCs have about the OW and the baby. She will be expected to make it all sound normal when explaining to them. She will be expected to bite her tongue and shrug it all off as something dad went ahead and did and he was entitled to do while at the same time raising the DCs with some sense of what is right and what is wrong.
I also predict this new relationship won't last very long. Someone who is as blind and deaf as this man seems to be to the feelings of others, including his own children's, is not a good candidate for any long term relationship.