The Lake Gardens is the biggest park in Kuala Lumpur on walking distance from KL sentral and Brickfields. It is worth a trip in the early morning when it is not too hot to walk around. We visited the park on a thursday morning and we felt we were the only one (except for a handful of runners).
Our Grabcar dropped us (my mother and me) at the entrance of the Orchid garden, where we had a beautiful view over the Petronas towers and KL tower. You feel so far away from the hussle and bussle of the city.
Also in the Lake Gardens: bird park, butterfly park, deer park, Hibiscus garden.
When you bring your kids, there are two nice and clean playgrounds.