There’s something about marrying someone who has children and not having the barest expectation that you’re going to be looking after them at some point… like, that’s crazy. When you marry someone who has three children you might best be prepared for the eventuality that you’re going to be taking care of them, either now or at some point in the future. There should at least be a point before the wedding takes place where you have that conversation, it doesn’t matter that he said that he “Isn’t looking for a mom for his kids,” as an adult around children you’re going to have to take on a role of responsibility even out of sheer proximity. It’s easy to get that, at 29 years old some people might not feel they’re ready for that responsibility, but then you probably shouldn’t be marrying someone with three children from a previous marriage.
Still, they’re her husband’s kids and he ultimately needs to handle the responsibility of having them, which means planning in advance. If he needed to be away for the weekend he definitely should have arranged something or had the conversation with her long before the upcoming weekend…