If you are travelling without kids, check out Little Governors camp. We did bring our 10 year old son but it was a bit scary at times for him and us! If you are going to go, this is the way to do it.
http://www.governorscamp.com/property-descriptions/governors-camps-masai-mara/little-governors-camp
Many camps have scheduled drives and lots of people driving together. Little governors gives you a dedicated driver who will schedule a drive as you like. Want to have a peaceful breakfast out in the Mara? Just tell your driver and he will organize your breakfast to be served under a Baobab tree after an early morning drive. I went with my best friend and our two sons and it was nice that it was only the four of us driving around. I'd see drivers from other camps with ten people in their cars!
Everyone else is right - fly into Nairobi, stay at Giraffe house (from the Safari Collection ... you can email Richard to make a reservation -
richard@thesafaricollection.com). Then you will fly to the Mara in a small plane. Little Governors will organize that for you. Then fly back to Nairobi and stay at Ngong House or fly out directly home. If you are staying for any time in Nairobi, the only thing I recommend you to do is go to the elephants at David Sheldrick. We stop in every time we are in Nairobi and I never get tired of hearing the stories of the rescued baby elephants. Also - very touristy - but dinner at Carnivore if you eat meat is hilarious.
Have a great trip! The Mara is the best place I've ever found for a safari.