Allen: if WWoHP is open during HHN, which is very, very possible, that would be your time to go to Ollivander's. In USF during HHN, Diagon Alley was minimally crowded and there were numerous PERSONAL Ollivanders shows available.
Oh, and of course it's at night. Chills.
Edit re the lighting ceremony: Parkscope is quickly debunking this possibility/idea, which is not a surprise. It's a novel idea to play around with, but ultimately it'd be very difficult to pull off considering everything.