I agree with Zachary that if roller coasters are a priority that you should go to IOA with Hulk and Dragon Challenge. Additionally Spiderman and Forbidden Journey are somewhat adventurous but they are the two best rides I've ever experienced thus far. I love the theming of the different areas and the food at Mythos is wonderful. On my last trip we didn't have a good experience at Confisco's restaurant but most people enjoy it. The lobby area, in particular, has amazing theming. Jurassic Park River Adventure gets a lot of criticism from people who think it could be better but it beats any other water-type ride I've been on. The other two water rides, Bluto's Barge's and Ripsaw Falls are great but necessitate your getting soaked, and Ripsaw Falls is hard to get in and out of...think Space Mountain. I'm not a huge fan of The Eighth Voyage of Sinbad and Poseidon's Fury, both show-type attractions.
BUT...I'm playing devil's advocate and Universal is calling to me also. The Monster Horror Makeup Show is terrific. T2-3D is an experience unlike any other with a mixture of live-action and movie footage which will delight Terminator fans. The Simpson's flight simulator is vastly entertaining for those that can stomach it. The new Springfield section of the park just opened and it looks amazing. The Mummy coaster is just awesome with it's unexpected backwards section and smart movie scenes. In that vein, Men In Black is the best shoot-em-up I've ever been on and has different Agent Jay endings based on your performance. Twister gets a lot of criticism, mostly because I think it doesn't have great repeatability but it's fun to do the first time. Oh, and how could I almost forget..Disaster is an attraction akin to the flood part of the Backstage tour at Disney but it got a huge upgrade a few years ago. Now it's hilarious with Christopher Walken doing a star turn as a movie director in the production of a disaster movie.
Ok, I've rambled on long enough and skipped lots of decent attractions (but covered most of the major.) Hopefully it gave you enough information to make a choice. I want to add that the quick service food at the Universal parks is not great. I would recommend eating at a restaurant. And I know your parents only have one day but if they are park commandos and have money like you (Dr. Jay Money), they could consider buying express and doing both parks in one day. I have had no problems doing this on many occasions in the past, depending on the closing times of the parks.