In the middle of the day? I thought that only tended to happen if they were doing something strenuous like exercise. Fairly sure that stuff will be later in the update. But then that's why I'm curious - because it's right at the start, at midday.
Well previously Ellie wanted the house to be empty to introduce Elena to Julia and to hang out at the pool without Dylan perving on them, so you may be right. Whether it's different with Dylan going to boarding school or not is going to be interesting, since it's only a small event - doesn't give much room for branching. I believe
Old dog mentioned something about the Ellie/Julia event having GW and Filthy route options, so that will also have an effect.