Two days. Hm.
Well, what's worked for us in the past is doing all the rides you want to ride on the first day and catching anything you missed and the parades and fireworks on the second.
I know it sounds simplistic, but that's about the best summary of what my husband and I do.
We hit all our favourite rides first by heading deep into the park and getting the most popular but most far away first, then working back.
If we still have energy that night we stay for the fireworks or (when we were there last ) the last showing of Fantasmic, and then the second day we spent shopping and puttering around, seeing all the parades we could, all the street performers.
Sigh. With the conversion rate I have no idea when we will make it down again. It costs us $1.55 for one US dollar - it's getting a bit better but still way expensive!
Have fun!