Yes it sucks for you and the dc but in all honesty the best thing you can do for you and dc is actually NOT Push this
I know that's not what you wanna hear but it's true.
You can't make someone be a parent when they don't want to be, legally, practically, emotionally or even financially in this country unfortunately
I very much regret pushing this with my own dd which merely resulted in pushing his vanishing out of her life down the road and led to him doing so as she started high school - the worst possible time!
How old are dc?
Also stop with the days out etc to make it up to them, it's not necessary and it'll knacker and skint you financially
Build yourself and the dc a support network elsewhere - single parent groups can be good for this
I met my best friend when dd was little she had a dd the same age and we were both single parents. We used to babysit for each other so we each got a break sometimes
You can't and shouldn't (as in for your own and dcs sake) attempt to rely on someone you clearly can't depend on you'll be fighting a losing battle I'm afraid
That will drain you faster than anything else