Information on Holiday in Kenya

Hello everyone, we are planning to visit kenya for holiday and we need your advise for few things. As i worked in kenya for 2 years and left kenya 4 years ago. I been to many places around kenya like Mara, Nakuru Naivasha, Sagana, Mombasa, Wasini etc. I want to know which could be the best safari place to explore and also if you can help me with someone who can guide us with best packages for them. Also our first plan is to explore safari for 3 days and another 3 days to stay in diani beach.  Meanwhile also looking for 6 seater vehicle with driver to take us where ever we want. So plz help with info so this trip could be a life time expeirnce for my friends.

Thank you,