Bobmn:
IF I understand the process, the first Covid 19 test is done before you get on your flight. In this case for these two it will be done in the US. If they test negative, they can get on the plane - If not they don't fly.
The tests while there are required to be done at an "approved" medical clinic. The quality/accuracy of those tests.....who knows. Then too, there have been a good number of reports of botched test results here in the US as well so........
As I understand it, IF they test positive on the 5-day in country test, they simply "quarantine" where they are hunting. That is the reason for the hunting locations have to be inspected/approved. Doesn't mean they stay in their room. Just means they have to stay on the property and can still hunt if they are asymptomatic and feel up to it.
For the 3-day prior to departure for home test, it's the same as leaving/flying from the US over.
Your last question about shots - the nicest part about Namibia is a very large part, mostly S of the Kunene River along the Angola/Namibia boarder and SW of the Okavango Rive Delta and Caprivi Strip area of the country, is outside of the general malaria risk area, especially so when outside the rainy season. Therefore, no "shots" are required and no anti-malaria meds either. Only thing I would recommend is having an upto date Tetanus shot. I also always take a 90-day supply of doxycycline "just in case". It can be used as a malaria preventative and treatment and also for treating tick bite fever and a few other illnesses.
I've read one medical article that made the claim that one possible reason the WuFlu hasn't devastated Africa as expected is the wide spread use of Hydroxychloroquine as an anti-malarial.
