Hi!
I'm off on a three day trip soon as well, and I only plan to spend a half day at AK. It is a beautiful park but I like the others better. I did a half day a few years ago over a spring break, and that is all you need. The rides we did (in order) are:
1. Safari (or get a FP and go back)
2. Kali Rapids
3. Dinosaur
4. Tough to be a Bug (FP maybe)
5. Lion King
That was about it! The park is giant, so it is a lot of walking, but you can really see as much or as little as you want. We had fun walking around the Jungle areas to see the animals, but it is up to you. The Primeval Whirl is something that I haven't been on yet, but it sounds interesting too.
The big things to remember at AK: Make sure to ARRIVE BEFORE OPENING! We were there for the rope drop, and it cut a good hour off of our wait times. We even rode on Dinosaur twice in a row with now wait! Everyone RUNS to the Safari, so you can always get a FP and go do the other rides in the meantime.
Also, DEFINITELY bring a poncho/garbage bag at Kali. You will get wet!
Hope that helps!
--Babka Gal