wow, i actually live in coeur d'alene,
The indoor water park is pretty cool, it's actually an addition to the bowling alley there.
It's called Triple Play.
Anyways, uh, I'd suggest going out to dinner at the Dockside, it's in the lobby of the coeur d'alene resort. THey have some good food there.
other than that, I spend most my "fun" time in post falls or in spokane.