It can be very tempting to wear flip-flops or sandals on safari, because its war or even hot, but this is not a good idea. When you are on game drives or bush walks always wear closed shoes. You can cut yourself of sharp grass or step into an insect that bites. When you are in the lodge and you walk on walkways open shoes are just fine, at least when its warm.
Check before you go how the weather will be and have for closed shoes a pair of sneakers or walking shoes with you and for in the lodge something easy and comfortable.