My husband has a conference in Orlando and my son and I are going to join him halfway through his trip.

We will have 3 days to either do Disney, Universal or something else around Orlando. (The conference is renting out Universal Islands if Adventure for one of our nights)

I don't plan on buying tickets until the day of or night before just so that plans can be fluid.

What are your best ideas/tips for a 12 year adrenaline junkie boy? I know for sure Hollywood Studios is on the list for one day because he wants to do the Tower of Terror.

I will be renting a car, so we have flexibility to come and go or go between parks.

For a time line idea…
Day 1 - arrive in Orlando around 12 and get the car from the airport
Day 2 - free all day, Universal from 7:30 pm - 11:00 pm
Day 3 - completely open

Disclaimer, I am not a Disney or Universal Junkie, but have taken the family enough times to the parks to be dangerous.

If I were going to plan a park itinerary around what you have provided, especially in October when the crowds are not a big, here is what I would do for a 12 year old adrenaline junkie.
Day1: Hollywood Studios - you do not need a full day to experience everything in the park. Tower of Terror and Star Wars are the main attractions. They have also redesigned the Rocking Roller Coaster as the Rocking Rollercoaster Featuring the Muppets. Depending on your budget you might look at purchasing the Park Hopper option. For a one day ticket it is almost double the price, but would allow you to move over to Magic Kingdom and experience the Not-So-Scary Halloween Party.
Day 2: Sea World - Believe it or not, Sea World has some excellent coasters. You should be able to do it all before heading to Islands of Adventure that evening. The other option for Day 2 would be Universal Studios. Since the company is covering the entry into Island of Adventure, I would not spend the money for the 2 Park option; however, you will run out of things to do at Universal Studios if you go early.
Day 3: Universal Epic Universe - The best and newest park for adrenaline junkies in Orlando.

Hope this helps!

If your kid is an adrenaline junkie, get a park hopper to do do Hollywood Studios and Epcot so they can do Cosmic Rewind at Epcot. I would recommend getting tickets in advance so you can purchase lightning lanes for the rides you want and minimize wait times.

The Halloween party at Magic Kingdom is a separate ticket. Magic Kingdom closes early on party days

At IoA, Velocicoaster and the Hulk will satisfy your adrenaline junkie! Hagrid's motorbike is also an awesome ride - have the kid sit on the motorcycle seat.

Epic is lots of fun, but not the most adrenaline inducing. It really only has 1 legit coaster with Stardust Races (Which is awesome and rarely has a super long line). Hiccups Wing Gliders is solid. The Monsters Unchained Dark Ride is a ton of fun.

The problem with Epic is there are only 11 rides and they are still working out capacity kinks so the lines can get crazy long on the popular rides. Also with FL weather can shut down several of the rides that are outdoors which increases the loads on the other ride. They've also shortened the park hours this year.

We went last November and with early admission because we stayed at a Universal Hotel, we were there from 9AM to 10PM.

This year we are going the same weekend and its now closing at 7PM which is crazy that they are closing that early. IMO Epic Universe is a park you also need to experience at night.

Epic is where you want to be.

FYI: Park Hopper doesn't get you into the Mickey's Not So Scary Party, it is a separately ticketed event. If its a night with the MNSSP, they will kick you out at a certain time so that the MNSSP can begin. I could be wrong, but I felt like I saw all/most dates are sold out for it already.

I was gonna suggest the party. We did the Christmas one a number of years ago, and I thought it was totally worth it. We didn't have a ticket to the park for the day, just the party. They do let you in early, and the park was not crowded so we enjoyed our favorite rides.

To add to the party, we did the Christmas party several years ago when our girls were elementary age. They were not interested in the parade and other stuff where the crowds were gathered but the effect of that was short to basically no lines at the rides. We were able to ride multiple times and were in the park until something like 2am.

Thanks y'all!

I knew that the Halloween party was a separate ticket, but they are all sold out anyways.

I have been considering the park hopper for our full day on Day 3. When we went a few years ago he loved Everest at Animal Kingdom, but there isn't much else he is interested in right now at that park. The park hopper could let us hit some highlights at least two different parks.

I'm not sure how the crowds will be because we will be hitting the end of marathon weekend. But hopefully they'll be pretty light by day 3.

Single rider line at Everest is often a near walk up, hop on the coaster, ride, repeat. Takes about 1 minute to walk thru the empty single-rider queue, and you might wait for 2 or 3 cars before you get to board.

We did the Mickeys Halloween Party last night. Lots of fun. Tons of candy. Biggest crowd I have seen for the Halloween party

ETA. Didn't see the sold out part. I believe it though.

That's exactly why I recommended it! Although, we've also done Halloween at Disneyland. The decorations and entertainment were so good. I imagine WDW does Halloween equally well.