Ofcourse you can so it all Solost! Practice makes perfect.
I think you're getting too tied up with thoughts of the OW and the kids. Let it go at the monment, as it won't do you any good. She probably is banging on about meeting them/caring for them etc to ingraciate herself more with you H, but thats becasue she's insecure bunny boiler - which we already know.
Instead tell you H that if the OW wants to help with the kids then she is to allow him to see them unhindered ona Saturday without demands to leave early. If she can manage this ( which is unlikely), then it's shows some form of understanding.
Your H should be careful what he wishes for. It is likely that they will not take to the OW once they know the truth, and also there respect and relationship with their father will suffer. If you said they could only meet if all children knew the truth, and the implications for there life choices etc - I bet he wouldn't be falling over himself for this.
I think you're being fab btw - and when I log on and see how strong your being etc, and his miserable whimperings ' oh this is so sad' blah blah I'm giving you a virtual high five !! Keep posting, it brightens my day to see you moving on.
I also want to say - that you really are in a win win situation. The more you detach the quicker you will be able to get on with your new life and all the exciting things that brings.
And if there is to be any reconciliation between you and your H , then he needs to get over the OW. He will be unable to do this if everything he is missing there he gets from you. Like chatting in car when is bored, etc.
Also how do you know she is under presure to have kids from her parents etc, looks down on SAHM etc - Probably becuase he has discussed it with you!!! Don't particiapte in these conversations. If he wants to talk about her then let him talk TO her. You ar enot avliable to be his own personal therapist!
Is it his parents or your parents that are helping with childcare? - What are his parents view of it all.