The evenings tend to be less crowded, so EP lines are usually pretty short. You should be able to do a lot the first day.
Definitely get to the parks early on Sunday and you should be able to do a lot before the crowds hit. If you are going to do Hagrids first, I recommend getting to the gets 1 hour before opening and head straight to Hagrids. You will still have time to visit Hogsmeade, FJ, etc, before the rest of the parks open. If you get to the gates right at opening, you will likely spend all of EE in the Hagrids line. In fact, if you can ride Hagrids at the end of your first day, that would free up all of EE for Hogsmeade...