HeadedGrid[
  finalSpacings:{_Integer,_Integer},
  finalBorderWidths:{{_Integer,_Integer},{_Integer,_Integer}},
  finalOptions_Association,
  headerCellGridder_Function,
  rawHeaders:{__String},
  dataCellGridder_Function,
  rawData:{__String}]:=
  With[
    {finalDims={Ceiling[(Length@rawData+Length@rawHeaders)/Length@rawHeaders],Length@rawHeaders},
     headerCells=headerCellGridder/@List/@List/@Characters[rawHeaders],
     dataCells=dataCellGridder/@List/@List/@Characters[rawData]},
    DataGrid[finalDims,finalSpacings,finalBorderWidths,finalOptions,Join[headerCells,dataCells]]];

(*An example with a few decorations:*)
HeadedGrid[
  {1,1},
  {{1,1},{1,1}},
  <|"dividers"->{"-","|","+"},"border"->"*"|>,
  DataGrid[{3},{6},{0,0},{{0,0},{0,0}},<|"background"->"-"|>,#]&,
  {"Su","Mo","Tu","We","Th","Fr","Sa"},
  DataGrid[{3},{4},{0,0},{{0,0},{0,0}},<|"alignment"->{-1,1}|>,#]&,
  ToString/@Range[31]]//AsString