Moana, I'm so sorry for adding to your pain. That wasn't my intention at all, but I can see how my words have hurt.
My situation was very different from yours - my husband was emotionally abusive, and a very angry man. Also, he didn't spend much time at home with us, which no doubt contributes to my son not remembering us together. He remembers things he did with me, but that will be because his father was either out, or didn't want to spend any time with him. Your situation sounds very different - you and your husband are able to be friends and he is a good father with a strong bond with his children. When my son was a toddler I worked out that his father spent only 2 - 3 hours per week with him/us during my son's waking hours.
What I was trying to say, and not succeeding, was that I understand your terrible pain and heartache for your children. Really I do, and your posts have reminded me of that. When I was going through that someone said something to me that I can now understand much better now than I did then. My heartache for my son was an adult's heartache, with an adult's knowledge of the world which is so much more comprehensive than a child's. As adults we have so much more life behind us to draw on, and we have an idea of how our future, and that of our children would be, and now that's all changed, and that loss of a potential future hurts. And in our heartache we project all of that loss onto our children. But a child's worldview is very different from an adult's, and in many ways that can let them cope much better, with less pain than we feel for them. If that makes sense. It's hard to explain. Our pain is for a loss that they're not even fully aware of.
Talking to my son over the years, I've come to realise that pretty much all of the things I broke my heart about over my divorce haven't even really entered his head, or if they have, then they've simply been to him the way his world is - a matter of fact, not pain.
Your pain is very real - physical, burdening. I'm so sorry about that, but it will ease over time.
You, and your children, and your husband will find a new "normal", and that can be a very good and positive normal for you all. And you can all make new memories going forwards - some new memories with you all together. You say that part of the reason for splitting now is so that you can remain friends instead of getting bitter. You can be friends, go out together for fun days with the children - the four of you together. Have meals together, go to the park together. Better your children have good memories of time spent together with divorced parents who are friends, than bitter and resentful parents who are married.
Stay strong.