A really good question Terrified, I don't know the answer so can only go by other people I know who've gone through separation and divorce. My sister had 2 S's with her ex, it was a fairly amicable split despite him having OW. They are all friends, even my sister and OW! They all spend Christmas together and go on hols together! He ended relationship with my sister but he's been reasonable throughout and has looked after her financially, always been there for S's.
My BFF
and her H split 7 years ago, he left for OW. They are still not divorced and he's never pushed for it. He sees kids every week, is friendly with her and supports her financially, he's never monstered or been difficult.
My H started affair this April this year, was indecisive for months but broke it off with OW and came to marriage counselling with me, decided he couldn't live without me, then started seeing OW again a month after declaring undying love for me, then left 3 weeks later and asked for divorce 2 weeks after that. After 23 years he wants shot of me asap, not seen our D's for 3 mths and doesn't seem too bothered by that, earns good money but has offered me a pittance and begrudges that, has frequently projected his temper at me, plus OW has been harassing me and is psychotic, def affair down. I do doubt it sometimes but I guess my divorce will be an MLC one!