Quoting Captain Lauren + ?:" That is how I see it, but he said it like Halloween for him. "
When it comes to decisions about our kids we have to take both partners feelings into account. If he is truly uncomfortable with it, than I would pull them out. Go do something together as a family, have fun, there's no need to start a potential argument over one little party. There will be other parties and other activities that the kids can do. Missing this party will not be the end of the world for them. I'm sure the kids will be disappointed but sometimes that is just how things turn out.