Disclaimer: I dont have kids and dont want them so prepared to accept my POV might be odd but...
...Just read a thread where a woman was talking about disputing maintenance costs with her ex and mentioned he never has his kids overnight, adding that its his choice.
Why wouldn't you just force them to have their kids? Im think if I were a mum I'd quite like to have half my time to just chill and have some downtime without my children? Or is it that when you have kids you cant bear to be wthout them?