Hey Teebin, does it say on what day that photo was taken in the image text?
As for the whole "exec kids" or "promo shoot" question, those kids DO remind me of being an extra (i.e. sitting around somewhere else while the shot is set up and being extremely bored) however we didn't see anything that would suggest a shoot in the WWoHP (lights, dollies, tracking, etc.) being brought into the area. Could they have done it at night after the park closed? Sure, but then you only have about 3 hours of set up AND shoot time (which, believe me, isn't a lot of time AT ALL) before you're in a night shoot, and then, forget it. To get all the equipment up and shoot at night and then film kids is a hassle. Not to mention how much you'd have to keep changing the lighting if you were shooting around dusk. If they shoot a promo, it'll all take place during the daytime (with maybe some pick-ups of Hogwarts at night). So, if they were shooting that day, it was all interiors and they had everything inside the 3 Broomsticks before the park opened. That's just my two cents.