As long as it’s not July you’ll be fine doing a one day trip if you have Express Pass (UXP)
The wait time in queues using UXP will, typically, only be about 33% - 50% of the posted standby wait time! Often even less!
It really looks like most everything you want to do is at IOA. However, if your son is a big HP fan then I’m going to recommend starting at USF. This is because Diagon Alley is stunning!! It is, IME, the best theme park “Land” anywhere!
You can do Gringotts, Olivander’s, get Butterbeer and etc… I’d try to see the 10am Tales of Beedle the Bard show. It’s the story of the Deathly Hallows origins and a great show.
Personally, Jimmy Fallon is my most hated attraction at all of Universal. You really need to be a BIG fan of the Tonight Show to enjoy it.
Also, there the BEST theme park stunt show anywhere is at USF - The Bourne Stuntacular. It’s a perfect all action show that a 13 year old boy should love. However, it won’t start until around 11am.
I’d enter and do Mummy, head to Diagon Alley for rides and exploring, then I’d check out Men In Black before catching the first Bourne show. Then I’d take the Hogwarts Express to IOA.
Do Hagrid’s anytime you see it posted under 70 minutes. You can explore Hogsmeade (which is smaller and sadly a little underwhelming) while doing Forbidden Journey.
Then I’d just walk counter-clockwise back to Jurassic Park for VC. I’d see if the Raptor Encounter is going on as you pass. If you don’t mind getting a little wet (not soaked) you should ride Jurassic Park River Adventure!
Then catch Spider-Man as you get closer to the park exit. (I’m a fan of Dr. Doom’s FearFall, but I understand it’s not for the feint of heart!)
There are a lot of great places to find snacks and meals in both parks as well!
Depending on when you arrive and when you plan to depart for the day you should be able to do all of this with no time concerns.
If you think you’ll be there near close, I’d recommend a second ride on Hagrid’s. Many of us love to hop in that queue 10 minutes before close. Since at that point it doesn’t matter how long you wait because the park will be closed when you are done. Plus, Hagrid’s at night is AWESOME! It’s like a totally different ride!!
Feel free to ask as many questions as you like about UOR!! There’s a few of us that are die-hard fans of the place and love helping people plan their first trips