Meeting the characters can be a lot of fun (yup, even for adults!). We met over 30 different characters over the course of our May vacation. The interaction is fabulous and very relaxed/low key (generally speaking, there's no huge lines or waits).
Despicable Me has stationery seating. The High in the Sky Trolley Train Ride should be okay for you, as well as Kang & Kodo's Twirl & Hurl and ET. Poseidon's Fury is a walk-through attraction that you might be able to do.
Take in the shows (Beetlejuice, Animal Actors on Location, Fear Factor Live, etc.). Watch the parade and the Cinematic Spectacular.
Go on a mission to eat lots of the unique snacks at Universal.....enjoy a Big Pink Donut in Springfield, sample Butterbeer (in all its various forms), have a Flaming Moe, etc.
Play some of the games in the Simpsons area (you can win some really nice stuff!).
Go in all the shops in Diagon Alley, including Gringott's Money Exchange. Buy a wand and cast all the spells.