Here is my 2 cents worth (and I TRULY mean TWO cents worth!
)If it were me I would leave them all in their normal positions as much as is possible and then have someone water them ONCE midway in your vacation. Better to underwater than overwater. This is assuming you don't have plants in a window that is going to be in warm/hot sunny window during that time - if so I would back them off as you suggested and then still go with the once routine.