Free, of course, I am not meaning to undermine your judgement at all, I hope it does not come across like that. It is a question of what you can cope with.
I think, what was the eye-opener for me, was the contact weekend after our mediation, which had been carnage and had a truly upsetting effect on me, that he was nicer than nice, really, it was almost hoovering. And it seemed to me like he had dumped his emotional distress on me, used me literally as an emotional punchbag, that is what it felt like, and having got it all off his chest, it was okay. And so there is a disconnect, and it was there in the relationship, where there would be this argument which came up over goodness knows what, impossible to fathom, which would leave me really distressed and he would be lighter than light. So, there is the question of which is the true him, and which is the true situation (and I am past caring, but that is another matter); but the outcome, regardless, is that the ground is always shifting beneath your feet. I have realised that I prefer my ground to be steady.
I would agree that the DC get something positive out of their parents getting along, but for me, and I am speaking only for myself, I balance that with (given that I don't trust the niceness) what I feel I can cope with. This is a brief chat at handover. I just would not put myself in the position of anything more extended than that.
The other point is that it is the appearance of normal and friendly, or a role you slip into/back into, and then out of again. It is not real normal and friendly; if it were, there would not be carnage behind the scenes.