USF opens 7 am for us tomorrow and we have express unlimited. Got 2 days to do both parks. Kids not huge on the bigger coasters.
Have Disney very very planned but done nothing for Universal and now wondering whether I should have!
Any tips for things to do early or does the express pass really mean we can just play it by ear for 2 days?
You can play it by ear! Express Passes are amazing, you will love it.
Oh! You will have a great time!
We had only a rough idea of what we wanted to do and where we wanted to eat during our stay at Hard Rock. We saw everything easily and got into every restaurant we wanted with minimal waits. The Express Pass makes everything so easy. Have fun! 
If you are planning on doing any spell casting in Diagon Alley, I find EE an excellent time to do that, as there are virtually no lines.