Both of those parks, and another at a school around 51st and 10th should be fine for some flat ground.
Columbus Circle, I only skate at night, when the homeless and/or crackhead lurkers replace the tourists and I haven't had a problem with the cops.
Pretty much all the mid town spots are busts from building security eventually, but there are so many in close proximity that you just skate on to the next one. Daytime, there are too many people around there, so those are also night spots.
I still live uptown and mostly skate spots up there, including Lennox.