Both Camellia sasanqua & japonica are rated for zones 7 - 10, with C. sasanqua being able to handle cooler temperatures. They prefer moist, acidic soil & part shade (during the heat of the afternoon). Here in the PNW they can be planted full sun. I would consider them a borderline plant for Idaho with sheltered siting in the shade.
Cornus florida is rated zones 5 - 9. They, too, prefer moist soil with a bit of shade in the afternoon as they are an understory tree. They aren't very tolerant of stress from heat, drought, salt & wind. However, I would plant one, depending on your site elevation & exposure.
Catalpa speciosa is rated for zones 4-8 & grown throughout the midwest. It is exceptionally tolerant of dryer conditions & full sun. They sucker though, so you'd have to keep up with that. Gorgeous tree!
