I have almost decide for the following itinerary:
Day 2:08/11/06:Nairobi - Masai Mara
Day 3:09/11/06:Masai Mara
Day 4:10/11/06:Masai Mara - Nairobi.
Day 5:11/11/06:Nairobi - Ngorongoro
Day 7:13/11/06:Ngorongoro - Serengeti
Day 9:15/11/06:Serengeti - Arusha - Zanzibar
Day 10:16/11/06: Zanzibar
Day 11:17/11/06:Zanzibar - Nairobi - Barcelona.
The operator is Eriken Adventure, seem very professional and nice