I would plan on being at IOA at opening of the first day and you will be able to do most of the big rides before it gets busy. Plan on spending the second half of the day at studios and do T2, Twister, Earthquake, they all swallow a huge amount of guests at one time. Second day start at studios and hit mummy and Shrek at opening and then back to MIB, jaws ET etc. Third day you can start and whichever park/rides you liked the best. We always arrive at least 45 min before park opening and often are let in early, sometimes we have had 2 rides on Hulk and 1 on Spiderman before the official opening time.