I think the whole issue of sc and holidays is complicated and utterly impossible to generalise about.
It depends entirely on the relationship between the sc and the nrp family (usually dad). There is a strongly held belief by some on this topic board - that sc MUST be treated in EXACTLY the same way as resident children regarding almost every aspect of their lives. I think that is completely unrealistic and impractical - and when we tried to employ that method - it was detrimental to resident children who have just as much right to a happy life.
There are so many factors that influence these issues. Money being the biggest practical obstacle. Followed by the nature of the relationship.
Money allows larger houses, own rooms that can be left empty between visits. Holidays abroad with multiple children in the most expensive time of the year. Lack of money (in the early years of our relationship) meant not going on holiday at all. Because we wanted to 'treat all kids the same' We just could never do it. 7 children going anywhere for a week - even camping, was not doable. (Despite the fact I could afford to take my Three and DH) However this came to a head after the year my Sc had had 2 Weeks in Sardinia with their Mother followed by Ten days in Turkey with Grandparents. We (DH/ me plus my 3 ) hadn't had a holiday for 3 years because of the 'principle' of sharing. A principle that actively disadvantaged MY children. So I put my foot down and booked a week in France for us.
We spoke to the dcs and explained that there was only so much money to go round and they had holidays abroad every year. Whilst their ssisters and brothers had none.
They completely understood.
As soon as we could afford it, we took them too. Which has been the situation for 7 years.
It also depends on relationship. Are the sc visitors who appear because they have to. ?(Mum wants space from them or dad has a court order) but given the choice, kids would rather stay home than spend EOW shuttling round the country to please parents - or are they an integral part of your family, with whom you are in constant contact with even when they aren't with you..?
Neither is 'wrong' - for many different reasons, the first type of relationship can just happen because of geography, infrequent visits, teenage dsc who aren't interested in visiting - along with the darker side of break ups like parental alienation and pure simple dislike of the step parent/ children.
All these set-ups influence the blended family relationship and that relationship is most profound between the Dsc and Step mother. None of this is set in stone and the nature of the relationship can change and evolve both negatively and positively.
My relationship with my Dsc has been very varied. In the early years they drove me potty as they were all terrible squabblers who lacked any sense of personal responsibility and were being coached into 'learned' helplessness by their DM. This played into Disney Dads narrative of them being incapable of so much as putting a plate in the dishwasher. - leading to conflict in our own relationship and my dread of them coming over EOW.
However - time has passed, I've got tougher, (with DH)!Court gave them the right to determine where they lived (huge parental alienation back story) and the eldest chose us.
So now it's all change again for the last few years with the two who live with us feeling nearly the same as my biological children. A much closer relationship.
So all in all. What I'm trying to say is that there are 'no rules ' that say Dsc HAVE to be treated the same. When it's possible, great - sometimes it's simply impossible and sometimes completely unrealistic.
And sometimes especially if the relationship isn't that close- as a step mother you simply don't want your step children in your face for three weeks. Especially if your DH is one of those who 'defaults' to letting you do all the cooking cleaning and laundry (because 'you are already doing it' - for your own !) ..
As a step mother you also have a right to have your feelings considered. It's NOT all about the kids. It's ALL about everyone.