Ugh, sorry they're putting you in this position! You're not doing them a favor, you're providing a service - it isn't rude or selfish to question why they aren't abiding by the contract they read and signed. I promise you if they had an issue with anything related to their pay or benefits at *their* jobs, they would not wait to bring it up let alone feel bad about bringing it up!

I would say something like, "Hey NP's, can we make time to sit down and talk about hours sometime this week?" and then, "I was hoping to touch base on guaranteed hours as outlined in my contract. I was left feeling a little confused when you guys went on Other Trip, and I'm sorry for waiting to bring this up, but I wanted to make sure we were on the same page before This Trip. Per our contract, (insert guaranteed hours blurb here). I also have a few articles handy that go into more detail about guaranteed hours/when they're in effect/etc. Again, just want to make sure we're on the same page, as I really can't afford to go without consistent and reliable payment (ideally they read between the lines here and understand that means "I'll be finding another job if it comes to that" lol) - if you have any questions, let me know!"

It sucks, but I would honestly be prepared for them to look at you like you're crazy (you're absolutely *not* crazy, but some parents are just living on another planet - that said, there are absolutely families out there who have done their research and want to be good to their nannies!). If so, I hope you're able to find something better super quickly!!

Last random thought: If guaranteed hours are covered in your contract and they still act clueless, big yikes, personally think you should pole vault out of there BUT...could, in the meantime, be worth asking whether they'd at least consider bumping up your hourly rate as a compromise? Then you at least make a tiny bit more between now and hopefully securing a new position!

Update us on how it goes - you got this!!!