Don't forget that parts of Zion are closed to vehicle traffic; you have to park and ride the shuttle bus. Plan to spend some time hiking, it's the only way to really experience the park. Zion was my personal favorite becuase you are in the canyon as opposed to looking down at it from the rim.
There's lodging in Springdale just outsize Zion. Also Kanab has an interesting old motel where all the film cast & crews stayed while making westerns in the area. Stayed there while on a bicycle tour of the area. It's kind of interesting to see the photos of John Wayne, Ronald Reagan, etc. eating in the coffee shop and lounging around the pool.