We've been to the South Rim several times. We stayed in one of the hotels in the little town outside the park once and inside the park the other times. There are a number of different types of accommodations in the park. We made the mistake of going in the beginning of January once and it was so cold we couldn't enjoy it. But it is beautiful any time of the year.
I also recommend Sedona (great quilt shop there) and Sunset Crater Volcano Park which is near Flagstaff. You can walk thorough the lava flow from volcano eruptions a thousand years ago. It's very cool. And if you drive farther out in the park, there are views of the painted desert. Have fun if you go - AZ is a wonderful place.