Why, we just dumped a 4 year old and a 6 year old on Gramma for 4 days just this past weekend! An Auntie was in attendance too, for good measure.
Thing is, the reason for going out is irrelevant - there's a way to do this politely, and there's a way to piss of gramma. Politely is simple, as I'm sure we all know:
"Hi mom. I need to get my big wet freak on with Tony, the well-hung bartender with the tickly mustache I met and humped senseless in the back room last Thursday at the club. Can you please take Junior and Little Missy this Thursday night for, oh, I dunno, three-four hours?"
And then there's not-so-polite:
"Hi mom. Sorry I didn't call before I came over. Here's the kids. See you in, oh, I dunno, three-four hours!"
Grammas are like everyone, I expect. Politeness goes a long way.
In hindsight, maybe Gramma doesn't need the TMI about Tony, huh? Sets the mood, tho...
Anyway: dumbgirl...not so dumb at all, when politely exercised (pun intended!).