I thought godparents were there to take over if anything happened to you, and to help in religious and moral education for those into that kind of thing. No one ever told me they were also free babysitting. Wish we knew, we could have saved a lot of money. 
Besides what everyone else said, it didn’t sound like any lives or income were in danger if they hadn’t gone out. Another reason the call was obnoxious.
I got ya topped. Sushi. With attendant soy sauce and wasabi.
(ow.)
Also, **Anastaseon ** totally rocks for calling her on the guilt trip. 
As for the next generation, the only ones breeding (or in any danger of doing so) on either side of our family are the ones who live in Oz. No fear of last minute babysitting guilt trips there. 
When our sitter falls through, one of two things happen:
I call my relations with “what are you doing tonight.” If they even sound like they have plans I say “nevermind, our sitter fell through and I was kind of hoping you’d be available.” If they say “nothing” I then ask - recognizing that nothing is a perfectly good thing to do and that its fine to say “gee, I was just hoping to stay home tonight and veg.”
Or, our plans fall through. Dinner reservations cancel.
What I ABSOLUTELY don’t do is tell the kids that Grandma is coming over before I’ve made arrangements. That way I don’t risk my lil’ darlin’s being disappointed because Grandma doesn’t drop her plans at the last minute because I want to go to a movie.
Just so you know, I first read the word I bolded as “pants”, which made me wonder how exactly you’re raising your kids.
My kids are at the age where they have a definate butt fetish, but Grandma does not encourage them in that fashion.