I didn't get the impression that you were the type to say bad things about your children's mother. But, I did sense she was that type, and knowing that about her, she might think you do the same. Your W can manipulate things to her advantage sometimes, so I was just sounding a little alarm when I read of the kids reaction to her. Forewarned is forearmed, as they say, even if it doesn't come to that.
Here is what I've recently heard from my kids about me:
* "Mommy doesn't like you" (from my son to me)
* "<Mommy's friend> called you a bad name" (from my older daughter to me)
* "Why do you help your son-in-law, you should help your daughter" (from my older daughter to my MIL, right in front of me)
* "We're more sad when we leave Mommy because we have the same blood as her" (from my older daughter to me)