As Skylock said there are two types of EP. One that allows you one Express ride per each ride and one that allows unlimited express rides. Since you only have one day to do both parks and limited hours because of the time of year, the one time use would be the best option if the goal is to see as much as possible. If you guys are the type of people who find a favorite and then are content to ride it over and over again, go with the unlimited option.
Unlike Disney you do not need to book or schedule anything in advance. You simply show your pass at the entrance labeled Express to enter Universal’s version of FP. Both types of EP allow you to ride all the rides, you aren't limited to choosing only three.
I’m going to assume you want to see as much as you can of both parks. First thing to note, the 27th is a Horror Night. This means that US will close early at 5:00. In addition, since it is fall, IOA isn’t open very late either. IOA closes at 8:00. Regular opening is at 8:00 Which means Early Entry for resort guests will start at 7:00, most likely at US since it closes early. So, you’ll have barely 12 hours if you do open to close.
I suggest arriving between 7:00 and 7:30. Here’s what a lot of people don’t realize, all guests can enter the park when it opens at 7:00 even if you aren’t eligible for Early Entry. They let everyone in the turnstiles. Then they have a checkpoint further in the park where they screen guests who are eligible to continue on to the rides. Even though you won’t be able to go past the checkpoint, there is still a benefit to arriving early. It gives you extra time to get ready for the day and puts you ahead of the crowds arriving at opening at the turnstiles. It’s a great time to take pictures, go to the bathroom, get breakfast or coffee, look in the gift shops, rent lockers, pick up a map and familiarize yourself or make a plan of attack. Then, as soon as they “drop the rope” so to speak you can be off.
There really isn’t a lot of planning needed with EP. You can pretty much just go in a circle and ride whatever you walk past that interests you. My advice would be to focus on US first, as it will get crowded in the afternoon with people arriving for
HHN. At US, the biggest draws are going to be Rip Ride Rocket, the Mummy, Transformers, and Gringotts. In addition, Despicable Me always has a long line because it is one of the few rides geared toward kids. If you are interested in doing this, either do it first thing (as EP can get longer than you’ll have time for) or do the Stationary Seating option which is always a walk on. MIB and Simpsons are also rides that get good reviews. I personally love MIB, but I know it isnt everyone’s favorite. Jimmy Fallon, Fast and the Furious, and ET are much less popular. Although, Fast and Furious is seeing long lines right now because it is the newest ride. However, I think many people find it a bit of a let down.
If you get an early enough start and time it right, you may be able to ride Rip Ride Rocket, the Mummy, and Transformers without using the EP. This would allow you a second ride on any of them that you wish to repeat using the EP later on. Basically, you’d make a circle and a half around the park, riding everything you are interested in once, and then reriding anything in the Production Central and New York areas you’d like to repeat. This would end with you at Kings Cross ready to board the Hogwarts Express for IOA. If you find yourself short on time or don’t care about reriding anything, you can simply walk to IOA after completing one circuit around US. The park gates are located close together.
At IOA, the main draws are Hulk, Spiderman, and Forbidden Journey. Kong and the water rides are well received as well. However, you do get wet on the water rides, so depending on the weather you may want to skip some or all of these. The barges especially soak you. The Dr. Seuss area is worth a look, very whimsical, and the Trolley Train Ride there offers great views of the park. Poseidon’s Fury and Dr. Dooms Fearfall are less well received. I personally really enjoy Poseidon’s Fury, but I realize many don’t share my fondness.
If you took the train over to IOA, you will end up at the back of the park when you arrive. The HP section will be to your right, Lost Continent to your left. It should be around lunch or early afternoon at this point, I’d avoid the HP area for the moment as it will be at its most crowded. With the EP, the crowds don’t really matter for riding, but there’s no EP for the shops which will be a nightmare to navigate through. You’ll enjoy HP better first thing in the morning or last thing at night. If you are interested in the water rides, now would be the best time to do them during the hottest part of the day. The water rides are located in Jurassic Park and in Toon Lagoon. Go through the HP section to get to them. Afterwards, you can simply continue on around the park riding what you wish until you end up back in the HP section where you can then explore it. If the castle show is still going, you will be able to see it as well. It only plays at night. If you don’t care about the water rides, I suggest making the circuit around the park in the opposite direction. Head to the Lost Continent first. This will still end with you back in the HP section, but you won’t have to fight your way unnecessarily through the crowds there in the afternoon.
A few notes:
Familiarize yourself with the attractions before going. At least in general. Know you probably won’t fit everything there is to do in in one day, so have an idea of which attractions are the most important to you or are not to be missed. Know which you are ok skipping over. You’ll be able to do a lot with either EP, but just not absolutely everything.
If you are a big Harry Potter fan, you may want to choose less attractions to experience outside of HP to give yourself more time in those areas. There aren’t a ton of HP rides, but there are lots of little things to do and explore like sending mail home by Owl Post, exchanging dollars for galleons at Gringotts, and casting spells. Plus so much more. Many people can spend the better part of a day just in the two HP sections alone. The train ride is also different both ways, so if you are a fan and have the time to ride it twice, do.
I recommend eating in at least one of the HP restaurants if possible. The theming and food are both very good, especially for quick service which will save you time. Fun options I like for table service are Mythos or Finnegans.
Consider which shows if any you will want to see as they only take place a few select times throughout the day and take up a lot of valuable touring time.
If you are ok with eating late, consider eating dinner in either Citywalk or at one of the nearby resorts. This will allow you more time to fit in more attractions in the park. Plus, there are some very good restaurants to try outside of the parks, especially if you are wanting a sit down meal. We love the Kitchen at the Hard Rock hotel, Cow Fish, and Bubba Gump. You’ve also got Toothsome for fun themed “character” dining and over the top desserts.