For various reasons, my mother doesn't want my father to get the yellow fever shot, so of the safari options below the yellow fever line, of which I think Namibia and Botswana are probably the best, what would you recommend as the best options.

Our goals are 1. to see as much varied big game as possible and 2. To stay in the most comfortable and luxurious accommodations on offer while still facilitating goal #1. This would be a family trip.

The flexible time frame would be mid-Jan to early April.