Show/Hide column title/sorting

I am trying to show or hide the title and sort arrows on a column based on my ajax response. This seems like something I should be able to do in fnServerData. I can't seem to find an example anywhere, has anyone managed to do this? This is as close as I've come:

                fnServerData:  function( sSource, aoData, fnCallback, oSettings) {
                    $.getJSON(sSource, aoData, function (json) {
                        if (json['error']) {
                            console.log(json); // placeholder
                        }
                        else {
                            var show_stars = json['show_stars'];
                            var stars_col_defs = oSettings.aoColumns[0];

                            stars_col_defs.bSortable = show_stars;

                            if (show_stars) {
                                // copy value from next column which is sortable
                                stars_col_defs.sSortingClassJUI = oSettings.aoColumns[1].sSortingClassJUI;
                                stars_col_defs.sTitle = 'Score';
                            }
                            else {
                                stars_col_defs.sSortingClassJUI = '';
                                stars_col_defs.sTitle = '';
                            }

                            // console.log(oSettings.aoColumns[0]);
                            // console.log(oSettings.aoColumns[1]);

                            fnCallback(json);
                        }
                    });

Thanks for any advice
Tony