I can see both sides of this.
I am a step mum and my kids go to their dads who occasionally has a lady friend.
My personal experience was quite horrendous, she picked up in everything I did, she said nasty things about me to her kids and then when she didn't get a response she began targeting my children. Told her children to call my son with asthma limp lung.
I did everything for her children to make them feel welcome, included them in everything. Her son doesn't eat anything but chips and processed foods. Which I really struggled with as we eat proper dinners, when asked what he has for tea it would be super noodles, nuggets, sausages, chips, burgers and that she gave vitamins so he didn't need fruit or veg.
I had them every holiday and every second weekend. I had them whilst my partner worked which was all the time including weekends. I was absolutely knackered.
I even got messages such as ' the children told me you've moved the Xbox to their rooms, I'm not happy that the kids are upstairs so you and her can snuggle downstairs, that's their time with you'
I seriously couldn't win, no matter how grown up the response to her was' it ended up splitting myself and my partner up.
Then the children hardly got to see him as he had work. It went to the occasional pick up to take them out for tea and drop them off again at 9pm.
We did end up back together, the children are actually here for the week this week. Rules changed though. I no longer put up with her constant 'righteousness' and 'bullying' I'm not here to be her punch bag or look after her children only to be attacked via text messages because she only saw one side. I'm not her personal babysitter.
They come over once a month for the weekend and extra time in holidays but not the whole holidays. I work at a school so always have the holidays off which worked out well for her for a while.
We have a great time, sometimes we stay in, sometimes we go out. I had to buy a people carrier as we couldn't get everyone in car, so had to use two cars for ages.
On the other side.. I've had my ex tell me he didn't want his kids for the two weeks he has off in holiday because he wanted his own time. He uses his other paid holiday in term time so gets that time to himself.
This all gets so complicated. People should always try and view both sides. No pre judgements, no assumptions. The kids will have a better time of it.
Anyway. Mine turned into a personal rant lol apologies!
See the thing is she wanted the help but then hated that her kids liked me. I think she was hoping it to turn out more like your experience, where they weren't so keen to come round.
Takes sensible communicative parenting and adulting.