there's plenty to do if you're 21. downtown pretty muchj from wednesday to sunday nights. alot of local bars and stuff. for tourist stuff, the twin falls, bogus basin in boise, go to jacckson hole, WY if you want to see yellowstone (the back roadway is going thru upper eastern idaho). there's lots to do, but you have to look it up. i'm not familiar with idaho.
if you're looking for good shoe shopping, you better go to salt lake or denver.
DON'T SEATTLE-IZE PORTLAND
Id stay in Spokane, if you're in that area...you're looking at Cor-de-lane (major spelling error) and Post Falls, ID...not much to do there at all. I went up there with my buddy for his cousins graduation, and they were really disappointing cities...we walked around downtown and found nothing to do. So we just hit up Spokane..much better.
coeur d alene is pretty sick. theres a really nice golf course (tiger woods is a member there), the lake is dope (rent some jet skis), but the locals around the area suck (Hayden lake was the headquarters for the aryan nation). if i were you i would just go west about 4 hours and kick it in seattle....but thats just my biased opinion.