Planning meals in advance HR

I have been following the overeating program, but have not yet planned my meals 24 hours in advance. My husband often asks me to lunch at the last minute if his schedule changes. This isn’t something we ever plan. He is not a planner, especially when it comes to meals so I can’t get him to plan ahead, but I don’t want to skip lunch dates because he isn’t a planner. Do you just find something at the restaurant that is similar to what you planned to eat or do you only go out to eat if you plan to go ahead of time? My brain might be making this seem harder than it is so I want to get some feedback to eliminate this “what if ” thinking. Thanks!