Organized, efficient guide.  For amateurs, worth the price ($159 for adult on Explorer Tour described here) to be guided safely and have appropriate supplies, including food and water.  The guide sets out a delicious picnic lunch keeps the squirrels from eating it.

 The  Explorer tour is challenging enough for the whole family, but manageable for those in reasonably good shape.  The South Kaibab trail itself is wide enough for horses, and stable, but not boring.  The edge (and a tragic fall) is just a step away if you are careless.  Great views.