They're still working through it.
Plus, they're still working out their adult relationship with you.
They'll be wondering whether to talk to you as their mother, or as someone like them.
If a friend of theirs broke up, they'd have conversations drawing out the emotional lie of the land and also the history of the break up.
I think that's some of what is going on here. The conversations you had with them will come from an uncertain - but not unloving - place.
You say you don't want them to take sides but ... is that true?
Even in your opening post, you catapulted from describing conversations with them where they were talking around the break up straight into 'They love him more!'
That is not fair.
Don't do that - to them or to you.
You are their mother. He is their father. They love you both. And will carry on doing that. Even if your husband fucked someone else. Because their relationship with you both doesn't have that dimension of sexual in/fidelity.
I think, underlying this, is a desire for your children to show a commitment to you that you feel your husband didn't. At some level, you want them as a substitute for your husband.
Given that your relationship with your husband had a sexual element and your relationship with your children is that you birthed and nurtured them, that is going to go very, very wrong, very, very fast.
If you start getting into the whole, 'You love him more than me,' thing, it will damage your mental health and your relationship with your children.
You have every right to bin your husband. You have every right to go on and have a bloody fabulous life. Be confident.
Don't undermine yourself. Don't create problems you don't need.