John Paul Chacha
Google
First off, you must absolutely go around the rim. If you don't do so, you'll be missing out on the best parts of the hike.
Longonot is one of those hikes that don't require a lot of planning; you just get up, drive to Naivasha and climb Longonot. Not to say that it is very easy; it is not a difficult hike, but some sections are steep and your knees will feel them, and the heat doesn't help especially when doing the rim on a hot January day.
If you have children above 7 who hike, definitely bring them along; this is a child-friendly hike. They might outpace you though; children seem to do well on this one, perhaps because of the low altitude and their ability to ventilate better.
Prepare for dust. This is a dusty hike unless you go when it is raining, after all, this is Naivasha.
Hiking boots would be great, but this is a relatively non-technical hike that you can do with almost any type of footwear, unlike some places in the Aberdares.
You don't need to hire rangers for this hike, you are unlikely to meet unfriendly wildlife and the trail is usually quite busy, especially on weekends - I'd say much busier than Kilimambogo, though I'd not recommend a solo hike here.
Total distance if you go around the rim is about 13 kilometres.
Overall, this is great weekend hangout for friends and family who love the outdoors.