I was a sensitive, fragile kid and do you know what was damaging to me? Seeing my mom stay in a marriage where she was frequently super unhappy and unable to be herself. I internalized the lesson that you have to stick things out no matter how shitty they get which is not a great way to approach dating. My sister and I both agree that while we love both parents as individuals, we would have all been happier if they'd gotten divorced. Sensitive kids pick up on their moms' feelings very easily- wouldn't you like it if the energy your oldest child was picking up was that of a mom who's strong enough to prioritize her happiness? You can talk to them about a divorce, bring them to a child psychologist to help them fully process, and they will be fine. Growing up with parents in an unhappy/incompatible marriage on the other hand does lasting damage.