We are generally park open to park close kind of people. AK used to be a short day, with the park often closing at 6 toward the end of the summer, we would usually stay until around 5:30, and then take a bus to the Poly for dinner at 'Ohana. After dinner, we would take the monorail over to MK, and then get a bus from MK back to POR.
With AK open late, getting dinner at 'Ohana AFTER AK isn't all that attractive, so we have moved our 'Ohana dinner to an MK night allowing us to use the monorail to get to / from dinner, and on our AK day we will spend the whole day in the park, eating supper there.
As for crowds, I don't expect the park to be any less crowded. It IS possible that the crowds will take a little longer to build up, making the park just a bit less crowded for the first couple of hours, guess we will just have to wait and see how that plays out.
Evening EMH, maybe. The used to have them. I remember doing evening EMH at AK around 2009 / 2010.