Full board at camp is not a style choice in the Mara, it is the only option — Narok and the gate villages are the last places you can buy your own food.
Narok, the last real town
About three hours out of Nairobi on the road in, Narok has supermarkets, cafés, fuel and the last reliable ATMs before the reserve. Everyone stocks up here; past it you are on camp catering whether you meant to be or not.
The gate villages
Talek and Sekenani have dukas, chai and simple nyama choma places serving drivers, guides and rangers. Cheap, unglamorous, and effectively the only independent eating anywhere near the reserve.
Full board, and what it does not cover
Camps and lodges are almost all full board because there is nowhere else to eat. Read what the rate actually includes: reserve entry, drinks, conservancy levies and the balloon are commonly extra, and the gap between 'full board' and 'all inclusive' is where Mara budgets break.
Chai, ugali and goat off the grill
The food everyone here actually eats: sweet milky tea drunk all day, ugali with sukuma wiki, and goat grilled over charcoal. You will find it at the gate villages and in Narok rather than on a camp buffet, which is aimed squarely at foreign guests.