If you're a parent with young kids, how long do you expect your other half to cover for you the day after a big night out? Do you expect to be child free all day? Sleep until lunch or whatever time you fancy?
I get SO fed up with DH not getting up, moping around, cancelling plans and generally feeling sorry for himself all day. Perhaps I'm being unreasonable though because although I drink when out with friends I don't drink enough to get a serious hangover and I'm never in bed past 10, and I wouldn't dream of cancelling plans with DC because of it. FWIW I usually try to dissuade DH from making plans for the next day because I know what's going to happen but he always insists it will be fine.
YABU being hungover means it's fine to opt out of any (self) planned activities and parenting for the day.
YANBU if you have kids you have to get your act together, get up at some point in the morning and stick to any plans you made.