I would not do Serengeti plus Ngorongoro plus Manyara plus Tarangire. I am not a big proponent of Manyara in any season, but lots of tour companies include it. Tarangire can be horribly hot and dusty in October, November, and January through March. To me, the Serengeti is great in any season except when mud makes vehicle travel too difficult. Ngorongoro should not be missed by anyone.