Unfortuneatley you dont have much time there. You must allow time for clearing customs and getting to your hotel as well as 2hrs check in time before departure.
On your first afternoon I suggest going straight to the Falls and spending the afternoon there, not really time for another activity.
In the morning you could do one activty, like helicopter flight, Livingstone island tour / devils swim, or Elephant back safari. I would recommend doing the Livingstone island tour.
