Congratulations. With that timeframe you should be able to do the marshmallow roasting, which is just North of Geyser Point about 6:30 PM. You can also see the electric water parade from the Geyser Point area when it comes by about 9:30. You can see some of the higher fireworks from there too, and they play the sound track, but it isn't a perfect view. They also do the nightly movies in the same general area, just South of Geyser Point on the grassy area near the boat rental dock.
Be sure to walk up and check out the lobby and follow the water from there through the inner courtyard towards the main pool. Down by the lake you can catch the Geyser going off every hour on the hour. The transportation boat dock is on the North side and from there you can hop on a red flag boat to MK, or the (usually smaller) blue flag boats do the loop on Bay Lake between WL, the CR, and Fort Wilderness. In the evenings there are usually two blue flag boats running, with one going clockwise and the other going counter clockwise. It can be fun to hop on and make a lap around the lake, and should take less than 30 minutes.
Enjoy your stay, it is a beautiful resort.