For the more serious photographers, a 400-500mm telephoto lens will work well, although a large lens might require a tripod, which cannot be used on the moving vehicle. A 2X teleconverter is useful to double the focal length of your lens.
You ought to pack rechargeable batteries, a charger, adaptors and converter, and some spare memory card, as these items are not available in the bush.
Please note that Botswana locals might not be as comfortable with cameras as you are. Rural people are often shy, although some may even request a fee in order for you to photograph them.
Also, not that you might want to, do not photograph any government or military building and installations, including soldiers, police and police buildings, post offices, banks, airports, border posts and railway stations.