Finally she said she feels i am taking up all of the kids time and she liked driving him to school.
My response was "OK" and walked away.
Well, "OK" is better than all of the other things you thought about saying. I think "OK" sounds like you dont really care about her feelings though. The other things seem to judge her feelings, this kind of negates them.
But I think validating them would be better. Maybe something like: "Hmm. I hadnt thought of your feelings about it; maybe we can set a schedule that will work for both of us?"