It's time to keep your household information to your self. If he asks how the kids are doing tell him they are fine. If they are not feeling well or side just let him know something generic like "Oh they're fine. Tommy had a little bug the other day, you know, a runny nose, but he's fine now". They gradually wean him off even that much.
That way he doesn't notice right off the bat that you are no longer sharing with him. Only share lots of good stuff, even if it's all exaggerated. Make it sound like nothing is going on and that the kids are great, absolutely great!
He won't miss that you are no longer telling him any problems. He may ask how something is going with a little one but I would brush over it and say it's better.
You cannot dictate what he does in his home while the kids are with him. If you try to do that he will retaliate and make sure to take away some choices you would like to make for your self. This can only backfire onto you.
He needs to be trusted to do good to his children. She won't hurt them or not take care of them while they are there hopefully.