We go every July, fortunatley we stay onsite, so have the room keys for the express line.
It will be crowded, and lines will be long,as this has always been the same over the last 6 years of going there, arriving at park opening will help getting rides done before the crowds start, my opinion would be to stay onsite for 1 night, and do both the parks over the 2 days, thats if you plan to do IOA as well.