1)Consult a physician who specializes in tropical/infectious diseases.There are many,many diseases that one can contract in East Africa...many of them fatal. Most of them are completely unknown to the typical US physician,so it must be an expert in "travel medicine" that you consult.Follow his/her advice to the letter,including advice about immunizations,malaria prophylaxis and what not to eat/drink.
2)Assuming that the folks you'll be staying with know the area well (that is,they've been there for a good while) follow their advice regarding safety issues to the letter.Remember that,among other things,the average woman's pocketbook costs the equivalent of nine months wages there.
3)Make sure you register at the nearest US Embassy/Consulate and stay in *constant* contact with them regarding safety issues and other matters.
Although my post might sound ominous to you,I assure you that it is possible to have a great time in that part of the world.The game parks are,IMO,among the most impressive places that I can imagine existing on earth.The dark tone of my post is because I had health and safety problems while in Tanzania.