We went to the South Rim last March. Based on Tom's recommendation we hiked down on both BA and SK. We are decent hikers but not nearly as good as we thought. We had every intention of going about a mile each way. But, we only hiked only about 3/4 mile down each, because we knew we would have to go back up, and up was difficult. Pay attention when going down and know your limits. Ooh-Ah Point is definitely a "must-see". Also good advise to be ready to go as soon as light enough and return before too hot. We stayed in Trailer Village and used the GC Shuttle service. We took our SUV and drove to the Tower and stopped at a lot of the look-outs along the way.
After spending 4 days at the South Rim (which was way too short), we drove to Williams, AZ and camped at the Grand Canyon Railroad. Our original intention was to ride the train. We didn't realize that it is a train trip back to the South Rim. Once we figured that out, we decided to book something different. We took the full day trip from Williams to the bottom of the Canyon. Only 1% of the visitors to GC visit the bottom. It was a great day and one of the highlights of our 6 month trip. Here is the link for your review:
https://grandcanyon.com/tours/south-rim-tours/the-inner-canyon-tour-from-williams-az/#
Enjoy your trip. It is exciting!