Moving to Kenya from the USA

It's generally only returning residents (excluding diplomatic staff & military) who can bring one container full of household effects, plus a vehicle, duty free.  If neither of you fit that category, then duty would apply and the duty, VAT, taxes and charges (based on cost, insurance & freight) generally amount to around 75% of the value of your contents, as determined by Kenya Revenue Authority.  For electrical goods, make sure that they will work on the 240 volt system, otherwise you will also need to buy step down transformers.

Concerning an aircraft; these are the criteria:

An aircraft is eligible for registration if it is—
Owned or Operated by
A citizen of Kenya,
An individual citizen of another State who is lawfully admitted for permanent residence in Kenya,
A corporation lawfully organized and doing business under the laws of Kenya and the aircraft is based and primarily used in Kenya,
A government entity of Kenya or political subdivision thereof; or Public enterprises and Developmental Associations of Kenya for own use only;
A foreign person who has leased the aircraft to one of the persons described in paragraphs (i) – (iv) above, provided that:
The aircraft may remain on the Ethiopia registry only for as long as the lease remains in effect; and certificate of registration includes the names and addresses of the lessee and, if different, the operator of the aircraft; and
Not registered under the laws of any other State; and in case of newly manufactured aircraft or certificate of deregistration when the aircraft has prior registration in other state.
The aircraft is not more than 22 years old since manufactured and engaged in passengers transport, unless the aircraft is used exclusively for general aviation purposes.
The aircraft holds an acceptance type certificate issued in accordance with part 5
Not more than 25 years of age since manufactured and engaged in Cargo transport or an Arial work.

Leisure boats and jetskis are subject to duty as far as I am aware.
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