If you pick just one, make it Genting + Batu Caves — many tours combine both in a single day since Batu Caves is on the way. That is the best value day out of KL.
Pick Malacca if you enjoy history and food more than rides. Saturday evenings have the Jonker Street night market, but weekends are also the most crowded. Go on a weekday if crowds bother you.
Skip Cameron Highlands on a short trip. Eight hours of driving for four hours of tea gardens is a poor trade unless the hills are the whole point for you.
Putrajaya is best as a 2–3 hour stop on the way to or from KLIA airport rather than a dedicated trip.
Whatever you pick, start by 8 am. KL's outbound traffic thickens after 9, and an early start is the difference between a relaxed day and a rushed one.
Doing beaches instead? See beaches near Kuala Lumpur. For your KL city days, start with a city tour or the full Kuala Lumpur guide.