A Kenyan visa is required for most citizens from most countries, including children. There are different types of visas. The main ones are single entry, multiple entry and transit visa, depending on your routing. Visas can be obtained directly on entry for nationals of most countries, please do check requirements for your country prior to travel.
For visitors to Kenya, the only obligatory vaccine is yellow fever, although you may want to consult your travel clinic about other shots such as Hepatits, Meningitis etc. Malaria remains a concern and it is recommended that you take prophylactics as well as precautions with insect repellent and by covering up at sunset. If you are travelling to Nairobi or to the highlands above 2,500 m, your risk is between low and none.
There is much to learn and much to photograph in Kenya, but please be mindful of respecting your position as a guest in the country and only photograph people and children, with their express consent. It is recommended that each person has their own camera on safari as the setting and wildlife will inspire you.
Medical insurance is recommended to cover the unlikely expenses in the case of an emergency or loss. Make sure to read all insurance specifications.