Exporting to Excel for hierarchical grid view i.e parent and child grid. The Output Excel should be looks like drill down report which child report can be hidden/visible.
You can check our online demo on exporting GridView's RowDetails - http://demos.telerik.com/silverlight/#GridView/ExportingRowDetails and try the same for the child GridView. You can use the childGridView.ParentRow.Item to get information for the parent row. The Output Excel should be looks like drill down report which child report can be hidden/visible. - This part of your feedback is not possible to be implemented.