It sounds as if you will be visiting only Ohau. In a long weekend you will not be giving your body time to adjust to the 5 hour time difference before you head back to the snow. Are you sure you can't stay longer? Because of the time change you will most likely be up very early your first morning or two. As far as sight seeing for a first time visitor I would recommend the Pearl Harbor complex, The Polyinasian Culture Center including the lovely night time Luau and show and touring the North shore where the big waves are. There is a public bus that you can ride all the way around the island for very little money. If shopping is on your list of must dos, Check out The Aloha Bowl Stadium swap meet on Saturday, lots of cheap T-shirts and other goodies to bring back home. Whale watching is wonderful this time of year. If you enjoy being in the water try to leave some time for snorkeling.
After enjoying all of that, sleep soundly on the plane on the way home to Wisconsin, then start planning your next trip to Hawaii to visit the rest (and best) of the Hawaiian Islands.
Have fun. Nothing better than a trip to Hawaii.