I think Charles is fine on a baby-- it sounds young enough and Charlie is a young-sounding nickname. I don't like Chuck either; it's very dated and hickish to me.
My dad's name is Robert (Bob), so I think of an old-ish person when I hear this. I also don't like the "bert" sound. I think Rob is fine as a nn, but Robbie The only Rob- name I like on young people is Robin.