One easy way to save money on a small group safari at campgrounds is to do it the "African way." That means you don't have a cook. Upon arrival at the campground, the guide makes arrangements with the cooks of other groups to buy cooked, delicious meals at a very low price. You even use their cutlery, linens, wine, etc. and get waited on by those cooks.
Previous posters in this thread have recommended very expensive safari operators. Having been on safari many times in both Kenya and Tanzania, I can reassure you that the amount of money you pay is not a great indicator of the quality of service you'll receive. Local people who run their own safari companies can do a fantastic job booking the same places that the every expensive outfits book, but at a much cheaper price.