You can do it with a macro quite easily. Are all the charts placed inline or do they have text wrapping turned on? Are there other graphics in the document that you don't want resized?
At it's simplest the macro could be
Code:
Sub ResizeGraphics()
Dim inShp As InlineShape
For Each inShp In ActiveDocument.InlineShapes
inShp.LockAspectRatio = msoTrue
inShp.Width = CentimetersToPoints(5)
Next inShp
End Sub