I lived in Nairobi for 3 years, and I cannot say the food is memorable - Paleo or not.
It will be hard to avoid corn and beans. Githeri - a maize bean mix - is big. Ugali, from maize flour, is another staple food.
The nyama choma, their BBQ, is quite tasty. Rear or medium is never really an option. Everything is well done whether you want it or not.
Sukumawiki, fried kale, tomatoes and onion, is rather good. I did not mind matoke, which is made from steamed plantain.
The regional cuisine varies quite a lot. Along the coast the food is pretty good, but I guess you will go upcountry.
You can easily get pumpkin, sweet potato and arrow root.
A lot of people have their own herb garden and if they have space, they will grow bananas, maize etc. I had banana trees, avocado trees, a mulberry tree and lots of herbs. Miss it!
Avoiding wheat is possible. You just skip the chapati and the tasteless loaf bread. You will have to give the mandazi a miss too - I admit I loved that stuff - flour, egg, butter, milk and a dash of sugar mixed together, then deep fried! Lovely with Kenyan tea.
Seed oils will be hard to avoid, but you can get palm oil.
Eggs can be a nightmare - I tried to eat boiled egg for breakfast, but about a third of those I bought had to be ditched because of rotten and/or toxic smell or taste. Sometimes the boiled yolk and white had the same white colour. Yes, the yolk was completely white. I do not know what they fed the chicken, but it was bad news.
Fasting is not a good idea. People will not take you seriously if you are skinny : ) I was told all the time that I had to eat more to get an ass. I only got a fraction of the marriage proposals of most other Western women.
Anyway, don't stress with the food. It is not a bad place and people know how to have a good time.
Eat, go dancing and enjoy yourself!