Some people do carry alot of cash - of course the risk is if you lose it then you do not get anything back.
However, the way I get round this is to put cash to lots of different places on myself and in my belongings - that way if I get robbed I don't lose it all. Travellers check are a good option but many people want cash - and you would have more bargaining power if you paid in US Dollars.
Some Safaris Companies and Hotels will only take foreign currency for payments.
You can get cash advances on credit cards from most banks located in the larger cities, but it will be in local currency.
Hope this is of some help.