Upvote:3
Our usual advice is to take plastic to the country and use ATMs (or a bank) when there. Make sure that your debit card does not charge excessive fees for foreign withdrawals. We have several threads on finding a bank for which this is true.
In your case, however, you may hit maximum withdrawal limits. You certainly can't get $7000 US (or its local equivalent) from an ATM in one day. Maybe in three days. I don't know if these limits would apply to a face-to-face withdrawal at a bank.
I discourage carrying large sums of cash. A legitimate safari will accept payment by card. I can't think of any way to spend that much money in "a few days" in Namibia that doesn't involve something dodgy.