@QueenoftheNimbleFlyingCat
OP brace yourself you will get lots of people saying YABU and I do think YABabitU but totally understandably upset. Think of free holidays and it's not that far. I do sympathise though as I would be devastated if my parents decided to leave like that!
I know everyone is saying YABU, but it’s not that simple, your op said you understand they have their lives, but the hurt is all about being excluded from the whole thing until it’s a done deal
I had this with my own mother. She’s told everyone else all about the house, the offer etc etc. I knew they were moving but she said nothing about anything until it was all done.
The hurt I felt was immense. Utterly cut me to the quick. I was winded. I understood about the moving, but not the exclusion from the information that everyone else had. I’m not a drama queen, I’m not one to tantrum etc. honest! 
I actually emailed her to ask her why I’d been excluded from knowing about the offer, the house, and even the address for over 2 weeks after she’d moved.
Her reply was “We were never that close.”
Ouch. I can’t tell you the pain. It was utterly devastating.
I have nothing to do with her now. For this and the fact she had some weird thing about my ds. She hurt him physically and then gaslit him. I think she resents me for something, but she’s so far inland in the kingdom of Denial, we’ll never know the truth
Worse is that she goes round telling everyone how much she helped me in this, that and the other, it’s the polar opposite of what she did.
So maybe we weren’t ever that close, but I just didn’t know it.
She won’t be getting any care from me, there are no holidays etc etc, she hasn’t seen my ds for over 8 years. We’re better for to tbh
So yeah, she has her life, can make her decisions but those decisions do have consequences and your in laws could have been more considerate and that’s what hurts