Nomad tours from nairobi to zanzibar

Hi, may husband and I will be going from nairobi to zanzibar this April with Nomad Tours. I’m looking for good advice on:

Packing list

Best duffel bags that fit in overland truck

Visas

Vaccination

Hote in naribi and Johannesburg

We are flying from Lima Peru to Johannesburg and then to Nairobi, so we have long flying hours

Thanks!!!