The fact that her mental health is of no concern to you seems really cold. I am sure this is a defense mechanism, and that's fine. She hurt you. But you will be in each other's lives even after this divorce, and even though your kids are almost all adults.
I have three siblings, and my parents divorced when I was 16. I am the oldest. You are going to have to deal with big life events together sooner than my parents did-- it was pretty easy for them to avoid each other at high school functions, but impossible at my wedding, for example.
I had a courthouse wedding. It was not the big deal it could have been. Looking back on it, I wish that I had had a church wedding with a nice dress and a nice reception. We could have afforded something better than the courthouse and lunch. But it just seemed easier to do a quick wedding, and it was.
Part of the reason it was so much easier is that my parents still absolutely hate each other after 17 years of marriage, and 13 years post-divorce. My mom emotionally cheated after my dad physically cheated, and I know all the gory details even though I wish I didn't.
I kind of wish I'd had a church wedding, but I can't imagine having one even today (they both remarried and divorced since they broke up, and were remarried-not-yet-divorced-again when I got married; you'd think there'd reason to hate each other after all these years) without all kinds of drama from my parents being forced to interact. It was pretty bad with just a courthouse wedding. My college graduation still brings my mom to tears, and they are NOT tears of joy, even though I got the first Bachelor's degree in her family. Dad doesn't have to deal with it, but I do. And it sucks. It taught me to keep my parents as far away from each other as possible. Thank god my MIL was there to runs interference at the courthouse.
Don't be the divorced father that maligns your ex wife at every opportunity. Be happy when she moves on, and treat her with as much respect as you can. That probably sounds like a big ask right now, but your kids will really appreciate it when you can be civil to each other.