Mine have never really spoken in 35 years. My mum made it clear that my dad was a terrible person which was very damaging when she followed it by telling me how similar I was to him. They made all sorts of mistakes which made life unhappy. Following their split I felt like I never belonged again. I guess I was a daddy's girl whose daddy wasn't there any more.
So, advice I would offer is
Very very important to maintain as good a relationship as possible with your stbxh.
Try to be as nice to each other and about each other as you can. No snidey comments.
Never make your dc feel guilty about spending time with the other parent
Try to remember that you and your dh chose to be together and the dc were born out of love. It's OK to tell them that the love is not there any more but I think important for dc to know that they were wanted and loved by both parents
Be open and honest with dc. They can sniff out lies and game playing very easily and it just makes them feel insecure.
Relationships with other family members such as grandparents and aunties etc become even more important so that the dc can talk openly about what's happening.
Make sure that other family members aren't being critical of the other parent.
Never ever use your child as a weapon to prove a point. I've seen parents let dc go to school without PE kit etc so that it reflects badly on other parent.
Your dc may need counselling or support from school. They may be fine. But be open to the fact that it's possible.
Listening to the dc is pretty important.
Good luck with it all. My parents did as bad a job as is possible and I've turned out OK. I'm convinced it wasn't the separation but the way it was handled that made it miserable. I've seen friends and colleagues do it brilliantly - spending important occasions together, helping each other out, etc. It's very much possible.