Mombasa beaches are pretty ordinary, and no true 5 star hotels and resorts. My suggestion would be to avoid the coast, and instead do a safari.

On arrival, you can get a hotel near the airport - Lazizi, Ole Sereni or Eka. Then start a safari the next day, ending the day you need to check in for your flight home. That evening, you can have dinner at Carnivore, and then head to the airport.

With safari's, there are two types:

1. Flying Safari - where you fly from park to park, stay in quality intimate camps, and use the camp vehicles and guides.

2. Driving Safari - you stay with the same driver/guide in a 4wd or safari van and drive from camp/park to camp/park. Kenyan roads are pretty crap, and a 200km journey can take upwards of 5-6 hours.

I would always suggest a flying safari.

Secondly for 6 nights, I would suggest two parks. The Masai Mara is a must (3-4 nights), and then the balance of the nights at either Samburu, Ol Pejeta, Lewa or Meru.

Let us know what your thoughts and budgets are, and then I could make some suggestions.