I've been to Kenya years ago. We were fine in Nairobi and when we were at the lodges. We went to the beach and ALL ie 30 odd people got severe diarrhea.
When I went to India 28/30 folk got diarrhea. The only ones who didn't were a couple who had an Indian GP who knew all about it and gave them some antibiotics. Yes. I don't know what!
My advice: Bring lots of toilet paper, immodium, oral rehydration sachets, possibly codeine.