Oh, Ranger! Story Tour Video Gallery
According to the Skywalk operators, which are not part of the National Parks Service, it is not necassary to book your tickets in advance. Busy season in the Grand Canyon is not until summertime, so it is not likely you would be running into any crowds either way.
Enjoy your trip to the Grand Canyon, it is a view you will never forget!
My favorite for sunrise would have to be Desert View. Most points near the Grand Canyon village have the sun in your face, whereas Desert View rests on a highspot looking down-canyon. As for sunset, I like to head along the Hermit's Rest road and stop along the way, with my favorite being Hopi point. If you look on a map, you will see that Hopi Point has one of the most panoramic views along the South Rim.
If you go out to Hopi point, you have to take a shuttle bus, and the bus route closes an hour after sunset.
The National Park Service does not operate rafting trips through Grand Canyon National Park. However, you may book trips through independent companies authorized to conduct business within the national park. A full list of companies is avaialble on NPS.gov.