Don't drive to the South Rim of the Grand Canyon, unless you really want to spend a couple of days in the Canyon, if you would like to have a day excursion to the Grand Canyon (and you can't really go to Vegas and not see the GC) take a helicopter tour from Vegas, ideally with a stop at the West rim.
Be aware of the small planes that do GC tours, don't think they have big windows and that makes it perfect for a day tour, they are small planes

On the other hand, it makes you appreciate legroom on Ryanair flights.
Indeed visit Sedona but make sure you have a hotel reservation, esp in the weekends, all hotels will be booked out in the weekends.
Don't plan to do a lot of walking in Vegas, it will be too hot.
Not sure if you have a specific reason to go to Phoenix, but at that time of year I know a lot of other places where I would rather be than Phoenix - what about San Diego or up Pacific coast highway ?