Just a heads up so you know going in. There is a huge Potter convention going on at Universal July 13th-17th called LeakyCon. There are over 2,000 Potter fans already registered for this convention. Most of the covention activites will be held at the hotel convention center but a lot of fans will be in the park, rather than attending all of the events. July 13th is the date for the private nighttime event in the WWoHP which should not effect you on the 15th. However, the fans will be in the park in mass on the 15th before heading over to the midnight DH Pt2 event for the film release at the City Walk theater.
So just so you know heading in, that I have no doubt that section of the park will be extremely crowded that week with LeakyCon going on. However, if you can get there before opening and be in line to get in at rope drop you should still be able to get in. And in a way, for your Potter freak daughters it might make it all that more fun for them, as they will be enjoying Hogsmeade with a ton of those who feel the same way they do. But it will be far more crowded than a typical July day, even if you factor out the film release, it will be the convention that will make it nuts.
