Hmmm, none!!! I am driving down at 2 am on the 15th so I can be there at 8 to ride SM. I really hope there is no dedication crap and they just let us all run wild to our beloved ride. I would say that whole weekend is gonna be crazy with that and the B-day. We are staying till tuesday the 19th in the hopes that it will be tamer monday and tuesday.
Ok, you ask which day will be MOST crowded in your subject line: Sunday, July 17th for sure! The actual anniversary of opening day and a Sunday in July. Crazy!
Saturdays are crazy EVERY weekend in the summer (this is why they are black out days on every kind of AP except Premium). Add to that the fact that it's the big 50th Anniversary Weekend, and you have a madhouse... A MADHOUSE!
Which day will be the LEAST crowded? Of the three given dates, I agree probably Friday, July 15. But the difference will be negligible... as ALL THREE DAYS will probably break attendance records!! Especially if the new Space Mountain will be open by then!