You can easily tour a few of Kenya's best safari parks with 5 days before proceeding to the beach. A combination of any of the following would work, all are suitable for your family set up:
- The famous route: Naivasha (1)- Lake Nakuru National Park(1)- Maasai Mara(2) OR Lake Nakuru National Park (1)- Maasai Mara (3). In October, Mara is not as crowded as in the months of June-September so no need to worry about it being extra busy.
- Samburu National Reserve(2)-Ol Pejeta Conservancy(2) OR Samburu National Reserve (2)- Ol Pejeta Conservancy (1)- Meru National Park (1)
- Amboseli National Park (2)- Tsavo East National Park (2) OR Amboseli National Park (2)- Tsavo West National Park (1)- Tsavo East National Park (1)
For options 1 & 2, you will need to travel back to Nairobi and take a flight to the Coast while for option 3, you can take the train to Mombasa as it will be closer then connect to your final destination either by road (to Watamu) or by air (to Lamu). Diani is another popular beach destination in Kenya you may want to consider.
After your beach stay, you can either fly out from Moi International airport in Mombasa or return to Nairobi and exit through JKIA.