I don't know where you're at, but there are only two CNS schools in Florida, but that American Martial Arts school has some concerning language. It could be that the guy is a terrible writer, but his bio is word salad. He lists a lot of things listed that should be easy to verify. He also lists John Will prominently on his BJJ page. There is no doubt that John Will is legit. But that doesn't mean that this guy is competent to teach BJJ. Also not sure what Champion Martial Arts is, so it's hard to know what a 5th degree black belt actually means in that style. Lastly, I'm very leery of language like, "studied extensively in many other... arts." Is that one month? 6 months? 10 years?
"Master Hammersley has trained and taught martial arts for over 35 years and opened American Martial Arts in New Smyrna Beach in 1985. Master Hammersley also is a 5th degree black belt in Tang Soo Do, 5th degree black belt Champion Martial Arts,1st degree black belt Kuk Ki Won Tae Kwon Do, as well as having studied extensively in many other forms of martial arts, most notably, grappling (BJJ) Hombu Akido, MMA and full contact fighting competition, as well as mastering many different styles and types of traditional weapons."
Looks like the other CNS school is loosely affiliated with American Martial Arts, but the instructor has a brown belt in BJJ under Jay Pages who seems to be a legitimate Caio Terra affiliate. I think it's worth checking the school out, if you're in the area.
To be very clear, martial artists have notoriously crappy websites, so it's worth checking them both out. But I think the Leader Martial Arts seems a little more solid to me and I like that he's got a clear BJJ affiliation and actual rank.
Other than that, I can't speak to Kempo or TKD. If it looks fun, knock yourself out.