The time it takes to visit the parks can vary greatly depending on factors such as time of year, crowds, FOTL access, etc.
As for other things to see, that depends a lot on what you guys are into. There are a lot of coasters around the Universal parks, so if you enjoy "thrill" rides, there is a lot worth checking out. If you prefer the more "tame" rides, your options are a bit more limited.
Spiderman at IOA would definately be something worth checking out as it is a very impressive ride. The combination of the ride vehicle and 3D effects is pretty interesting. I also Really Enjoy the Poseidon's Journey show.
At Universal Studios, The Mummy is very impressive and fun, though be warned it is techincally a coaster. (But no more intense than BTMRR). the Show elements however are quite impressive. The Simpsons ride is a quite enjoyable motion Simulator ride.... and Men in Black can be a ton of fun as well. (think cross between a traditional ride and TSM/Buzz Lightyear w/ it's shooting elements). If you don't like spinning however, be warned since MIB does spin you several times.
Since you've never been to Universal, i'd also recommend checking out ET if you can. The Indoor Queue area is very impressive with it's own little show (if you pay attention), and the Pine smell from the indoor line has almost the same memory recall as the Orange Smell from Horizons does to old-school Disney people. The ride itself is a tad dated these days since it was one of Universal Orlando's opening attractions, but it's a cute little family ride and worth experiencing at least once.
If we knew what kind of rides you enjoyed, it might help us in pointing you to things definately worth checking out.