If I get this right, you are going to stay in Sedona and drive to the Grand Canyon for a day trip?
Save your gas IMHO.
It will take you nearly 3 hours with driving the 115 miles, getting thru the gate and, if lucky, get a parking spot. Then maybe a couple of hours of staying at the main area, giving it a Chevy Chase and about 2 3/4 hours to get back to Sedona. You will have a short midday view of a washed out from the bright sun episode. You will not even be able to take the bus out toward the west end.
You can tell people you have BEEN to the Grand Canyon, but you have not SEEN the Grand Canyon. To appreciate the color, depths accented by shadows, etc that you will only get in early morning and late into sunset you have to STAY at the Grand Canyon.
Janss has excellent comments on Sedona itself. The area around there also needs early morning and evening views for the colors.
Having spent much time at the Grand Canyon and, God willing, be there again this Fall I really kinda get passionate about the place - have seen it in all kinds of weather and situations including a white out snowstorm.