If you want to pan without holding the Ctrl key you should make the RadDiagram's ActiveTool to be the PanTool.
About the selection - if you want the selection to be activated when the Shift key is hold you should handle the RadDiagram's KeyDown event and to check if the hold key is Shift to activate the RadDiagram's PointerTool. Analogically - if you want to continue panning without the Ctrl key after the Shift is released you should handle the KeyUp event and implement the same logic to return the ActiveTool to PanTool.
You can check the attached project to see the approach I described.
All the best,
the Telerik team