About a two hour drive north of Boise is a great little resort town called McCall. It has a beautiful lake, great mountain biking, and camping. There is also some decent restaurants.

Also, Sun Valley is a great place to visit. It has a lot of tourists though - not vintage Idaho.

Most of southern Idaho is very, very dry. Were it not for irrigation, the land would be very barren.
You might check out Craters of the Moon National Monument, east of Boise. The surrounding terrain is that of a relatively recent lava flow, with cinder cones and ice caves. One thing about it, the wind has a tendency to blow hard all day long.
Farther east is a Dept of Energy instllation, which is closed on one side of the road but on the other side, one of the original atomic breeder reactors is open as a museum. I found it fascinating.
To the north, around Coer d'Alene you will find mountains, lakes, and forests.
Some impressively sharp mountain summits can be found if you get off the beaten path and onto the back roads. You should check with the National Forest Service before going for maps and a list of the rules. Several years ago all vehicles and pack trains traversing National Forest land were required to have a shovel, ax, and bucket in the party. I drove out there several years ago on a camping trip. We had a full sized car with plenty of room for luggage, so I stuck in a garden shovel, my ax, and our cook kit was packed inside a big bucket like container. A forest ranger saw the Ohio tag on my car and I am sure he thought he had himself a pigeon. He pulled in behind me as I was getting out my fishing rod. He told me the rules and asked me if I was aware of them. I said yes; I read the stuff before I came west.
I pulled out this long garden shovel and stuck in the ground at my feet, then hauled out this huge bucket, and then I asked him if wanted to see my ax. He said "No" and left. Good thing, because I had smashed the handle of the axe splitting a huge hunk of fire wood earlier that morning.
I could have handed him the head of the ax and asked if he had a handle.