About as easy as Kenya gets with children — a shallow reef-protected lagoon, short distances and no dawn game-drive schedule — with the tide as the one thing you genuinely have to plan around.
The reef makes it safe, the tide makes it complicated
The fringing reef keeps the lagoon flat and shallow, but at low tide the water pulls back a long way and the exposed reef flat is sharp with sea urchins in it. Swim on the rising tide, and put reef shoes on children before they go anywhere near the flat.
Kids' diving
Diving The Crab, Kenya's oldest dive base and a PADI five-star centre operating from Nomad on Diani Beach, runs a dedicated children's diving programme alongside its adult courses. Ask them which level suits your child's age before you book, as the courses are strictly age-banded.
Skydiving takes them from age 12
Worth knowing if you have a teenager: Skydive Swahili accept tandem passengers from 12 with parental consent, jumping from 10,000 feet and landing on the beach, with the whole thing taking three to four hours from arrival.
Monkeys are not pets
Colobus and vervets move along Diani Beach Road and through hotel grounds all day. Vervets in particular will take food straight out of a child's hand and can bite — do not feed them, and keep balcony doors and food shut away.
Getting around with children
Tuk-tuks are the local taxi along the strip: cheap, everywhere, and with no doors or seatbelts, which is worth thinking about with a toddler. Boda-boda motorbikes are not an option with small children; hotels will arrange a car for longer runs to Ukunda or the ferry.