Age incurs great respect among Kenyans and Tanzanians -- mzee means "old man" in Kiswahili but is actually an honored title of respect -- so older travelers are generally treated with politeness. However, there are no special discounts or provision for senior travelers. The countries don't have any specific restrictions aside from health risks, which can be avoided with the right preparation.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.