hi congrats on your newly start family.
We have been to Tanzania for a short safari in 2010 dry season. 4 person 1 4x4, private tour.
Here are some info that I can share:
1, we used focus-in-africa tour, they are not only a tour business, also a charity organizer. This way the cost is kept down. But not sure if they also handle Kenya, you need to check.
2, it's a billion dollar business in TZ and KY for the safari, with hundreds of tour companies. There is a HUGE price difference. Now let me try to explain why:
3, basically whatever you pay, the weather, and the terrain are the same. This means, when it rains, you get wet or cannot even open the roof for shooting, the shitty roads to and in the parks will give you an African massage all the time, and mosquito bites will risk malaria for everyone. What money makes a difference is: hotel accommodation OUTSIDE the park; where you have camping, log, or full hotel; food everyday, fresh cooked or picnic lunchbox; and condition of the vehicle you ride.
4, for the two of you, to hire a private vehicle results in, very likely, additional charges. Camping is even better, 'cause they have dedicated camping sites, it's not that wild and definitely safe during nights. And can save you lots on budget.
5, for 14 day safari, I believe you can go yo Serengeti and stay in for a couple of days. No idea how it is handled inside that huge vast park, as far as i know, there are individual camping sites inside the park just like other ones outside the smaller parks.
6, we took one of the cheapest tours, that is, 100usd per person per day. However, nothing felt cheap. It was about as expected, plus we had a wonderful cook and a wonderful driver who is very experienced. It's important, because you need a good guide to get you to the location of a kill in time, otherwise you only see ruins of a zebra with a crowd of vultures.
7, I dont know when are you planning to visit, but please check first, the high season might be more expensive, but it sure has its reasons. We arrived one week after the great migration, there were only about 100 zebras left in the whole ngorongoro national park... I would need to pay another S$5k to see the migration again...
Overall speaking, enjoy and good luck