Ok, my oh ex is similar to your dh ex
This is how you manage bullies like her:
Ignore the bad and reward the good
NEVER EVER EVER reply or engage with any text that is even slightly snarky
In fact, block the number and get her to email only. That way you can compile evidence in case you need to use it in court at some point. Emails are also less intrusive if you switch off the notifications.
The holiday, take the initiative and book what suits you so that you don’t get fucked about, and neither do the kids. If that means you all go away and the kids stay home, that’s on the ex. Very easy to explain. “Your mum said no, so we listened to her and made other plans. Perhaps she’ll say yes next time. You’ll have to ask her”
We had oh dc basically tormented and brainwashed by the dm to the point that the child refused to come at the last minute and it was obvious that the dc actually enjoyed every second of twisting the knife on behalf of the mother. Oh has had to submit to the perma dramas of the ex over every other holiday/plans/event since year dot. Even when they were together she was like this. She’s ruined every holiday/event possible by antagonising her dc in order to upset them and therefore upset everyone around them. It’s a lottery every single morning you wake up with the dc in your home, because if the dm has got to them, the dc will be wound up to the eyeballs and we wake up to batshit crazy in da house. It’s awful to experience and utterly excruciating to watch this manipulation done to a child. Her own child! Phone gets removed overnight, WiFi “breaks” but you can’t live like that, it’s exhausting and so pointless at the end of the day!
So we went away without the child last year and it was actually the most relaxing holiday ever.
This year the invitation won’t even be made, there have to be changes made for things to change. The dc is well old enough to see that if they blindly do the bidding of the mother, say the awful things they say, and hurt others for fun that there have to be changes made. I’m hoping that it’ll have the desired effect and the ex stops the games/the dc learns not to let the dm pull the strings any more. It’s a harsh lesson, but the sooner the dc learns independence, the sooner they will be safer from the maliciousness of the mother.
Some people really are awful. They have kids and then they use them as weapons to get what they want.
Remove all the drama from your lives and be really clear with the kids that the way you live is simple, loving, respectful and kind. If their m wants to play games at their expense, you’ll not engage at all, and if she says no, you’ll take her word for it, and seek legal advice
Your dh kids are old enough to tell a judge what they want, so you could apply to courts and get the holiday dates agreed by court order
Our issue in our household is that if oh went the court route and got it all formalised, the ex would basically torment her dc into refusing to cooperate and oh would in effect have to drag his dc through things against their will which would be utterly destructive
It would mean that that oh would become the bully... and he’s absolutely not that. In our case oh has to wait till dc eyes open...