I second the water rides and resort hopping is one of my favorite things for a rainy day. I still have several sets of Mickey ponchos, the cool yellow ones!
My very first experience at WDW was while there for a conference. I had spent 4 miserable days and nights doing presentations at the Dolphin, everytime I wanted to go to the park another Sr Exec would want a demo, finally we had 4 hours before we had to head to the airport, and it was raining. I grabbed one of my guys and we did a whirlwind tour of MK in the rain. No lines and we got on EVERYTHING in 3.5 hours. Back to the Dolphin, change in the restroom and off to the plane.
After that I was hooked ! ! !
Land safe and have a great time.